Disk drive having a thickness equal to an IC memory card

ABSTRACT

A compact card type disk drive includes a housing (21) for accommodating a disk for storing data, disk drive for rotating the disk, a head assembly for writing and reading data to and from the disk and an electronic circuit including at least an interface circuit (39), the latter three being accommodated in the housing. A connector (42) connected to the electronic circuit is fixed to the outside portion of the housing (21). The electronic circuit preferably contains a read/write circuit (36) and a control circuit (38). The housing (21) preferably includes a lower base (22) and an upper cover (23), and a printed circuit board (14) is disposed along the inner wall of either one, or both, of the base (22) and the cover (23). The outer dimension of the plane of the disk drive is preferably about 85.6 mm×54 mm, and typically, the outer thickness is 5 mm. Preferably, one connector (42) is disposed on either one of the minor sides of the housing (21). The connector (42) is disposed at the substantial center of the housing in the direction of its thickness and is fixed to one of the minor sides of the housing (21) which opposes the head assembly with respect to the disk.

This application is a continuation of application Ser. No. 07/946,359filed Oct. 29, 1992 now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a disk drive that can be utilized as anexternal memory of a computer system, and that utilizes a magnetic diskor a magneto-optical disk. More specifically, it relates to a wholeconstruction of a disk drive having a housing of a credit card type, acircuit assembly thereof and the structure of each of the variousmechanical components within the above housing.

2. Description of the Related Art

Generally, disk drives, e.g., magnetic disk drives, having at least onemagnetic disk utilized as a recording medium, have been in practical usein various areas including computer systems as non-volatile memorydevices. Further, in recent years, improvements in the technology of themagnetic disk drives, such as increasing the magnetic recording densityof the magnetic disk, have been realized, leading to down-sizing ofmagnetic disk drives per se. On the other hand, computer systems, etc.,have been becoming more compact, lighter in weight and lower in powerconsumption, as represented by a portable personal computer, owing torecent rapid development of microelectronics.

Though down-sizing of the technology of the magnetic disk drive hasprogressed recently as described above, the dimensions are still toolarge, the weight too heavy and the power consumption too high if amagnetic disk having a diameter of 2.5 inches is utilized. Therefore, itmay be difficult for the current magnetic disk drives to be applied tothe above portable personal computer for which compactness, lighterweight and lower power consumption are required. To meet thisrequirement, a magnetic disk drive utilizing a magnetic disk with adiameter of 1.89 inches has been announced in public recently. Thismagnetic disk drive surely has smaller dimensions than the magnetic diskdrive with a diameter of 2.5 inches. However, in such a magnetic diskdrive comprising a magnetic disk with a diameter of 1.89 inches,down-sizing of the magnetic disk drive has been attempted by using theprior art without making any improvements. Therefore, a problem occursin that the dimensions of the above magnetic disk drive, especially thethickness or height, are still too large for the disk drive to bepractically used as a portable device (nowadays, it is generally wellknown that the lower limit of the thickness thereof is as large as 10mm). Moreover, another problem occurs in that such a magnetic disk drivecannot have sufficient durability against mechanical shock caused byexternal factors, such as a fall of a portable device, whichincorporates such a disk drive.

Further, a modular unitary disk file subsystem has been disclosed inU.S. Pat. Nos. 4,639,863 & 4,860,194, wherein an elongated printedcircuit board is directly attached to the side of a housing including ahead and disk assembly so as to attain thinner dimensions. However, aconcrete thickness value in such a construction is not described inthese prior arts. Moreover, even though the thickness of the disk drivecan be reduced successfully, a new problem would occur in that the areaof the disk drive including the printed circuit board and the housing isenlarged more than usual.

Taking these conditions into account, in a known portable personalcomputer or the like that is currently in use, an integrated circuit(IC) memory card is provisionally utilized, rather than a magnetic disk,so that the required dimensions and weight can be attained. Thespecifications of this IC memory card have been standardized recently{the standard specification of JEIDA (Japan Electronic IndustryDevelopment Association) and PCMIA (Personal Computer Memory CardInternational Association)}, where the thickness or height of the cardis defined as 5 mm or 3.3 mm. A card satisfying these standardspecifications is sufficiently thin and sufficiently light, andtherefore the above card can be suitable for application to a portablepersonal computer, etc., in view of dimensions and weight.

However, presently, there are two significant disadvantages in the aboveIC memory card as follows.

First, computer systems utilizing the IC memory card are extremelyexpensive. More concretely, the cost per megabyte thereof is severalhundreds of dollars/MByte, which is several times higher than a computersystem utilizing flexible disk drive and is several times higher thanthat of hard disk drive (i.e., magnetic disk drive).

Second, the whole storage capacity of a computer system utilizing theabove IC memory card is not always sufficient to comply with the currentrequests of users. Nowadays, an IC memory card having a storage capacityof approximately 1 MByte is mainly used. The storage capacity of the ICmemory card will be increased up to the order of several MBytes to 10MBytes in the future. On the other hand, presently, in the idealportable personal computer, a memory system having more than 40 MBytesis actually required. Accordingly, the computer system utilizing theabove IC memory card cannot substantially satisfy the currentrequirements for storage capacity. Moreover, in the near future, theabove storage capacity that is required by users will be expected to beincreased more and more. Therefore, it will be difficult for the storagecapacity of the IC memory card to catch up with the required storagecapacity, even with the progress of IC memory technology taken intoaccount.

As described above, if a magnetic disk drive according to the prior artis to be utilized for a portable personal computer, it will besufficient in respect to the cost and storage capacity, but it is notsufficient in respect to the dimensions, weight, power consumption anddurability against mechanical shock. On the contrary, the IC memory cardcurrently utilized for portable personal computers is sufficient inrespect to the dimensions, weight, power consumption and durabilityagainst mechanical shock, however, the cost of the IC memory card is tooexpensive and the storage capacity thereof is not always satisfactoryfor the users. Therefore, in order to realize a suitable portablepersonal computer, a memory device that has both the advantages of themagnetic disk drive and the IC memory card is strongly desired.

As a strategy for overcoming the above-mentioned difficulties, it isconsidered to be effective to utilize the specifications of a type IIIPCMCIA. In this type III PCMCIA, the same dimensions as type I and typeII are defined in respect to plane directions, while the thicknessdimensions are allowed to be a maximum value of 10.5 mm. If oneconnector conforming to the type III of PCMCIA is provided, a cardhaving the thickness of 10.5 mm can be inserted into two different kindsof slots of the type I and type II arranged in a vertical direction.

As described above, if the specification of the thickness dimension isdefined as 10.5 mm, a disk drive of a card type can be realized by usingthe prior art without any improvements. Actually, a device having athickness of 10.5 mm has already been announced. However, thedown-sizing of the device is necessitated in personal computers,particularly notebook type personal computers, and therefore, astructure such that the two slots are arranged in a vertical directionmay be disadvantageous in terms of down-sizing. On the other hand, inpalm top type personal computers, only one slot can be provided in eachpersonal computer. In other words, it is now difficult for memorydevices in all areas that IC memory cards are utilized to be replacedwith magnetic disk drives. Therefore, it is strongly desired thatmagnetic disk drives having outer dimensions conforming to the type I ortype II, i.e., disk drives with a thickness equal to or less than 5 mm,be realized.

SUMMARY OF THE INVENTION

Accordingly, an object of the present invention is to provide a magneticdisk drive of lower cost and sufficient storage capacity whichsimultaneously has the advantages of an IC memory card such ascompactness, lighter weight, lower power consumption and sufficientdurability against mechanical shock.

A further object of the present invention is to provide a magnetic diskdrive that has the same thickness as the IC memory card, e.g., 5 mm, aweight lighter than 70 g, stability against mechanical shock of morethan 200 G and resistance to external magnetic fields of more than 1kGauss.

To attain the above object, the disk drive according to the presentinvention comprises a rectangular housing, inside which is contained atleast one disk that stores information, a disk driving means that forcesthe disk to rotate, a head assembly that performs read/write operationson the disk, and electronic circuitry. Also, at least one connector thatis connected to the electronic circuitry is fixed outside the housing.

Further, the above electronic circuitry includes an interface circuitthat allows communication with an external host system, a read/writecircuit that receives read signals from the head assembly and provideswrite signals to the head assembly, a servo circuit that controls theoperation of the magnetic disk and head assembly, and a control circuitthat receives control signals from the host system via the interfacecircuit and provides the control signals to the read/write circuit andthe servo circuit.

Further, the above head assembly includes a magnetic head that executesreproducing/recording operations corresponding to read/write operationsof information at a predetermined position on the magnetic disk, asupporting spring mechanism that supports the magnetic head, an arm thatsupports the spring mechanism, and a rotary type actuator that forcesthe arm to rotate in either direction and the magnetic head to move to apredetermined position on the magnetic disk.

Preferably, the above housing has a base at the lower side and a coverat the upper side, and electronic components that constitute the aboveelectronic circuitry are assembled on at least one printed circuit boardwhich is located along either one inner wall surface or both ofrespective inner wall surfaces of the base and cover. More concretely,the above printed circuit board is composed of a flexible printedcircuit board. Alternatively, both the base and cover are made of metaland are also used as metal based printed circuit boards.

Further, preferably, the disk drive according to the present inventionhas outer dimensions in plane directions of approximately 85.6 mm×54 mmand has a thickness of less than 8 mm, typically 5 mm.

Further, preferably, a plurality of insertion guide portions, whichallow said housing to be inserted into a slot of a host device so thatthe disk drive can be in an operative condition, are provided onpredetermined portions of the respective sides having longer dimensionsof the housing.

Further, preferably, only one connector is attached to a portion of oneof the sides with shorter dimensions of the housing. Furthermore, theconnector is located in an approximately central position in respect tothe thickness direction of the housing, and is attached to either one ofthe sides having the shorter dimensions of the housing, in a positionopposite to the head assembly across the magnetic disk.

Further, preferably, the base and cover of the housing have couplingflanges, respectively, that extend outward at the outer peripheralportion thereof, excluding the portion where the connector is located,the housing being formed by jointing the above coupling flangestogether. In this case, the base and cover are made of a metal includingiron, a metal including aluminum or resin material. Furthermore, thejointed coupling flanges are preferably covered with at least one frame,that is constructed so that it serves as an insertion guide rail, asealing means for ensuring that the inside of the housing remainsclosed, or a buffer means that protects the housing from a mechanicalshock.

Further, preferably, the disk driving means includes a spindle motorthat is located at the inner portion of the disk so that the disk canrotate. Further, the above spindle motor has a first fixed shaft that isfixed in a predetermined position within the housing so as to supportthe disk rotatably, and has a pair of first bearing means that are fixedat the upper side and lower side of the first fixed shaft, respectively,so as to hold the disk.

The above head assembly has at least one magnetic head 27 that executesreproducing/recording operations corresponding to read/write operationsof the information on either surface of the upper and lower surfaces ofthe magnetic disk 24, at least one arm 28 that supports the magnetichead 27, and an actuator 29 that forces the arm 28 to rotate in eitherdirection and the magnetic head 27 to move to the predetermined track onthe magnetic disk 24.

The head assembly further has a rotary type actuator 29 that forces thearm 28 to rotate in either direction and the head 27 to move to thepredetermined track on the magnetic disk 24, a second fixed shaft thatis fixed in a predetermined position within the housing, and has a pairof second bearing means that are fixed at the upper side and lower sideof the second fixed shaft, respectively. Furthermore, the above firstfixed shaft and second fixed shaft are constructed to be fastened to thebase by fitting them into the base.

Further, preferably, the first fixed shaft and second fixed shaft haveflange portions on one portion of the first fixed shaft and second fixedshaft, respectively, wherein the flange portion of the first fixed shafthas a diameter approximately equal to or larger than the average spanbetween the pair of first bearing means, and the flange portion of thesecond fixed shaft has a diameter approximately equal to or larger thanthe average span between the pair of second bearing means.

Further, preferably, the first fixed shaft at the disk and second fixedshaft at the actuator are rigidly coupled with the cover in respect tothe thickness direction of the housing. More concretely, one end of thefixed shaft at the disk and the fixed shaft at the actuator are fixed tothe cover by spot welding or by adhesion.

Further, preferably, the spindle motor has a fixed shaft that fixes thespindle motor per se in a predetermined position within the housing, apair of bearing means that are fixed around the fixed shaft, a spindlehub that has an outer portion engaged with the central hole of themagnetic disk and has an inner portion mounted in the first fixed shaftrotatably via the bearing means, at least one rotor magnet that is fixedto the spindle hub, and at least one stator coil that is fixed to thebase. In this case, the rotor magnet is located between the position ofthe inside diameter of the magnetic disk and the position of the outerperipheral portion of the bearing means in respect to the radialdirection of the rotor magnet.

More concretely, the spindle motor is an outer ring rotating type motor,and the rotor magnet has a thickness larger than the average distancebetween the pair of bearing means at the upper and lower sides, and therespective centers of the magnetic disk, the rotor magnet and the pairof bearing means are located in the approximately same position inrespect to the thickness direction of the housing.

Alternatively, the spindle motor is a flat type motor with an axial gapin which a magnetic gap is formed in the axial direction of the fixedshaft of the spindle, and the magnetic disk is engaged with the outerperipheral portion of the rotor magnet, and the inner peripheral portionof the rotor magnet is rotatably supported by the fixed shaft of thespindle via the bearing means, and the rotor magnet is constructed suchthat it also serves as a spindle hub.

In both of the above two kinds of spindle motors, the magnetic disk ispreferably fixed to the spindle hub by adhesion.

Further, preferably, a load/unload assembly is provided inside thehousing that allows the magnetic head to be loaded in a predeterminedposition on the magnetic disk and the magnetic head to be unloaded fromthe position thereon in connection with inserting/removing operationsfor inserting the housing into a slot of a host device and for removingthe housing from the slot thereof. Furthermore, a locking assembly isprovided inside the housing that forces the magnetic disk and actuatorto be locked mechanically in a predetermined position in connection withthe above inserting/removing operations.

Further preferably, the actuator includes a flat coil that is located inone end of a moving part of the arm (carriage) opposite to the magnetichead in respect to the second fixed shaft of the actuator; an upperyoke, a lower yoke and side yokes that are located around the flat coil;and a permanent magnet that is located in either one or both of theupper and lower yokes. In this case, a magnetic circuit is constitutedfrom the upper yoke, lower yoke, side yokes and permanent magnet.Furthermore, either one or both of the upper and lower yokes areconstructed such that the width of each central portion of the upper andlower yokes is larger than the width of each remaining portion thereof.

Further preferably, the actuator is a moving coil type actuator thatincludes an upper yoke element having a plurality of first bent portionsthat are bent downward at approximately right angles, respectively, anda lower yoke element having a plurality of second bent portions that arebent upward at approximately right angles, respectively. Furthermore, aclosed magnetic path is formed by combining the upper and lower yokeelements with each other.

Further preferably, the disk drive according to the present inventionfurther comprises a retraction magnet that is provided in the outerfringe part of the actuator to force the magnetic head to be inretraction, and a retracting yoke that is located around the retractionmagnet and has a gap in which the retraction magnet is placed.

More concretely, the thickness of the gap is changed in the direction ofdisplacement of the magnetic head so as to retract the magnetic headtoward a predetermined position. Typically, the thickness value g of thegap is changed approximately with a relation of approximately 1/(x+x₀)in respect to the displacement value x of the magnetic head.

Alternatively, the area of the portion, where the retraction magnet andretraction yoke overlap with each other in the plane included in a spacetherebetween, is changed in the direction of displacement of themagnetic head so as to retract the magnetic head toward a predeterminedposition.

Additionally preferably, the disk drive according to the presentinvention comprises a rectangular housing which includes one magneticdisk that is equal to or less than 4.8 cm (1.89 inches), a head assemblyhaving two magnetic heads that execute read/write operations, andfurther comprises one connector that is connected to the electroniccircuitry outside the housing, and has outer dimensions in planedirections of approximately 85.6 mm×54 mm. In such a construction, themagnetic disk and two magnetic heads are constructed such thatperpendicular magnetic recording can be executed. Typically, each of thetwo magnetic heads is a unitary magnetic head that has a body comprisedof flexible thin sheet. Alternatively, the magnetic disk and twomagnetic heads are constructed such that longitudinal magnetic recordingcan be executed, and each of the two magnetic heads includes a headslider with a predetermined flying height.

BRIEF DESCRIPTION OF THE DRAWINGS

The above object and features of the present invention will be moreapparent from the following description of the preferred embodimentswith reference to the accompanying drawings, wherein:

FIGS. 1, 2 are views showing an example of a disk drive structureaccording to a prior art;

FIGS. 3, 4, 5, 6, 7, 8 and 9 are views showing a first preferredembodiment of a disk drive structure according to the present invention;

FIG. 10 is a view showing a second preferred embodiment of a disk drivestructure according to the present invention;

FIG. 11 is a view showing a third preferred embodiment of a disk drivestructure according to the present invention;

FIG. 12 is a view showing a fourth preferred embodiment of a disk drivestructure according to the present invention;

FIG. 13 is a view showing a fifth preferred embodiment of a disk drivestructure according to the present invention;

FIG. 14 is a view showing a sixth preferred embodiment of a disk drivestructure according to the present invention;

FIGS. 15, 16, 17, 18 and 19 are views showing a seventh preferredembodiment of a disk drive structure according to the present invention;

FIG. 20 is a view showing one example of a change in the enclosure partof tongue portions in the seventh preferred embodiment as in FIG. 17;

FIG. 21 is a view showing another example of a change in the enclosurepart of tongue portions in the seventh preferred embodiment as in FIG.17;

FIG. 22 is a view showing an eighth preferred embodiment of a disk drivestructure according to the present invention;

FIG. 23 is a view showing a ninth preferred embodiment of a disk drivestructure according to the present invention;

FIGS. 24 and 25 are views showing a tenth preferred embodiment of a diskdrive structure according to the present invention;

FIG. 26 is a view showing an eleventh preferred embodiment of a diskdrive structure according to the present invention;

FIG. 27 is a view showing a twelfth preferred embodiment of a disk drivestructure according to the present invention;

FIG. 28 is a view showing a thirteenth preferred embodiment of a diskdrive structure according to the present invention;

FIG. 29 is a view showing a fourteenth preferred embodiment of a diskdrive structure according to the present invention;

FIGS. 30, 31, 32, 33 and 34 are views showing a fifteenth preferredembodiment of a disk drive structure according to the present invention;

FIG. 35 is a view showing a sixteenth preferred embodiment of a diskdrive structure according to the present invention;

FIG. 36 is a view showing a seventeenth preferred embodiment of a diskdrive structure according to the present invention;

FIG. 37 is a view showing an eighteenth preferred embodiment of a diskdrive structure according to the present invention;

FIG. 38 is a view showing another example of a frame applied to a diskdrive according to the present invention as in FIG. 32;

FIG. 39 is a view showing a first preferred embodiment of a fixed shaftconstruction of a disk drive according to the present invention;

FIG. 40 is a view showing a second preferred embodiment of a fixed shaftconstruction of a disk drive according to the present invention;

FIG. 41 is view showing a third preferred embodiment of a fixed shaftconstruction of a disk drive according to the present invention;

FIG. 42 is a view for explaining the relationship of the diameter ofeach fixed shaft and the average span between each pair of bearing meansas shown in FIG. 39;

FIG. 43 is a view for explaining bias means on the outer ring portionsof bearing means as shown in FIG. 39;

FIGS. 44, 45 and 46 are views showing a fourth preferred embodiment of afixed shaft construction of a disk drive according to the presentinvention;

FIG. 47 is a view showing one example of a change in a fixed structureof a shaft and cover in the fourth preferred embodiment as shown in FIG.46;

FIGS. 48 and 49 are views showing a fifth preferred embodiment of afixed shaft construction of a disk drive according to the presentinvention;

FIG. 50 is a view showing a first preferred embodiment of a wholespindle motor construction of a disk drive according to the presentinvention;

FIG. 51 is a view showing a second preferred embodiment of a wholespindle motor construction of a disk drive according to the presentinvention;

FIG. 52 is a view showing a third preferred embodiment of a wholespindle motor construction of a disk drive according to the presentinvention;

FIG. 53 is a view showing a fourth preferred embodiment of a wholespindle motor construction of a disk drive according to the presentinvention;

FIG. 54 is a view showing a fifth preferred embodiment of a wholespindle motor construction of a disk drive according to the presentinvention;

FIG. 55 is a view showing a sixth preferred embodiment of a wholespindle motor construction of a disk drive according to the presentinvention;

FIG. 56 is a view showing one example of a change in a disk fixingstructure in the sixth preferred embodiment as in FIG. 55;

FIG. 57 is a view for explaining means for correcting an imbalancephenomenon in a disk fixing structure;

FIG. 58 is a view showing a first example of a change in a frameillustrated in FIG. 38;

FIG. 59 is a view showing a second example of a change in a frameillustrated in FIG. 38;

FIG. 60 is a view showing a third example of a change in a frameillustrated in FIG. 38;

FIGS. 61, 62, 63, 64, 65, 66 and 67 are views showing one example of alocking construction of a head assembly of a disk drive according to thepresent invention;

FIG. 68 is a view showing a first preferred embodiment of a spindlemotor construction that allows a disk to be fixed in reverse in a diskdrive according to the present invention;

FIG. 69 is a view showing a second preferred embodiment of a spindlemotor construction that allows a disk to be fixed in reverse in a diskdrive according to the present invention;

FIG. 70 is a view showing a first preferred embodiment of an actuatorconstruction of a disk drive according to the present invention;

FIGS. 71, 72 and 73 are views showing a second preferred embodiment ofan actuator construction of a disk drive according to the presentinvention;

FIGS. 74 and 75 are views showing a third preferred embodiment of anactuator construction of a disk drive according to the presentinvention;

FIG. 76 is a view showing a fourth preferred embodiment of an actuatorconstruction of a disk drive according to the present invention;

FIG. 77 is a view showing some additional embodiments of an actuatorconstruction of a disk drive according to the present invention;

FIGS. 78, 79, 80 and 81 are views showing one improved example of afirst preferred embodiment of a whole spindle motor construction as inFIG. 50;

FIG. 82 is a view showing another improved example of a first preferredembodiment of a whole spindle motor construction as in FIG. 50;

FIGS. 83 and 84 are views showing one preferred embodiment of a headretracting construction of a disk drive according to the presentinvention;

FIG. 85 is a graph for explaining the relationship between thedisplacement of a magnetic head and the gap value in FIG. 86;

FIG. 86 is an enlarged perspective view of FIG. 84;

FIG. 87 is a model of rotation utilizing magnetic force for explainingthe principle of a head retracting mechanism in a disk drive accordingto the present invention;

FIG. 88 is a graph showing the result of actual measurement of torque ina head retracting mechanism of gap changing type;

FIG. 89 is a view showing one example of a head retracting mechanism ofarea changing type;

FIG. 90 is a view showing other example of a head retracting mechanismin a disk drive according to the present invention;

FIG. 91 is a view showing another example of a housing constituted fromthree separate elements; and,

FIGS. 92, 93, 94 and 95 are views showing an example of a disk drivehaving a whole structure in which one disk and two heads are assembledin a housing according to the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Before describing the embodiments of the present invention, the relatedart and the disadvantage therein will be described with reference to therelated figures.

FIGS. 1 and 2 are views showing an example of a disk drive structureaccording to a prior art. To be more specific, FIG. 1 is a front viewshowing the whole structure of a disk drive according to a prior art,and FIG. 2 is a schematic diagram showing separately a circuit assemblyand a mechanical assembly of the disk drive in FIG. 1.

In this case, a magnetic disk drive 1 has two housings, i.e., an innerhousing 6 and an outer housing 7. As shown in FIGS. 1 and 2, a magneticdisk 2, a spindle motor 3, a magnetic head mechanism 4, a head IC 5constituting an amplifying circuit 5a and the like are contained in theinner housing 6, which is enclosed in the outer housing 7. Further, in aspace between the outer housing 7 and the inner housing 6, an IC 8constituting a read/write circuit 8a, an IC 9 constituting a controlcircuit 8b, an IC 10 constituting a positioning circuit 8c and an IC 10'constituting an interface circuit 8d are incorporated. Furthermore, aconnector 7' is attached in the outer housing 7.

Such a magnetic disk drive 1 is usually stored in a predetermined place,and is carried and connected to an external host system, such as a hostcomputer (not illustrated) by utilizing the connector 7', as occasiondemands. Further, information can be read (reproduced) off the magneticdisk 2 and the information can be written (recorded) on the abovemagnetic disk 2, utilizing the read/write circuit 8a.

More specifically, in the above circuit configuration, control signalsS_(c) and address signals S_(a) are sent from the host computer to theinterface circuit 8d via the connector 7'. Further, the control signalsS_(c) are input to the control circuit 8b, and status signals S_(c)indicating the current status of the magnetic disk drive 1 are issuedfrom the control circuit 8b to the interface circuit 8d. Also, theinterface circuit 8d is coupled to the positioning circuit 8c, whichdetermines the position of the magnetic head mechanism 4 on the magneticdisk 2 in accordance with instructions from the host computer. Theinformation of the above position read by the magnetic head mechanism 4is sent back to the positioning circuit 8c as position signals S_(p),via the amplifying circuit 5a, so that accurate positioning can beperformed by means of servo control. Further, power is supplied to allthe above circuits, together with any other associated circuits.

In the above-mentioned prior art, the inner and outer housings 6, 7 forma double structure, where the disk drive 1 has the inner housing 6 thatincludes main mechanical components, and has the outer housing 7 thatsurrounds the inner housing 6 and that includes mainly electroniccircuitry. Owing to such a double structure, the lower limit of thethickness H₁ (FIG. 1) of the outer housing 7, i.e., the height dimensionof the disk drive 1 is likely to be limited to a certain minimum value.Consequently, it becomes difficult to realize a disk drive having athickness as small as that of an IC memory card and having overalldimensions that conform to those of the IC memory card, according to theprior art as illustrated in FIGS. 1 and 2. Therefore, a disk drive inwhich the outer dimensions thereof, the whole thickness in particular,can be reduced remarkably by providing a housing of a single structure,is highly desired.

FIGS. 3, 4, 5, 6, 7, 8 and 9 are views showing a first preferredembodiment of a disk drive structure according to the present invention.To be more specific, FIG. 3 is a perspective view showing an outerappearance of a magnetic disk drive and the dimensions thereof; FIG. 4is a perspective view partially showing the construction within ahousing; FIG. 5 is a schematic diagram separately showing a circuitassembly and a mechanical assembly illustrated in FIG. 4 separately;FIG. 6 is an exploded perspective view showing the construction of FIG.4 in more detail; FIG. 7 is a sectional front view of FIG. 4; FIG. 8 isan enlarged sectional view taken along a line I--I of FIG. 4; and FIG. 9is an enlarged sectional view taken along a line II--II of FIG. 6.

In the first preferred embodiment, as illustrated in these figures, amagnetic disk drive 20 comprises a single rectangular housing 21 that isconstituted from a base at the lower side and a cover at the upper side.Further, the housing 21 has outer dimensions in plane directions ofapproximately 85.6 mm×54 mm and has a thickness of less than 8 mm,typically 5 mm or 3.3 mm; namely, the above magnetic disk drive 20 canhave the same size as that of the currently used IC memory card of typeII of PCMCIA.

In this case, unlike the prior art as shown in FIGS. 1 and 2, onemagnetic disk 24 preferably having a diameter of 48 mm or 1.89 inchesthat stores information, a disk driving means 15 that forces themagnetic disk to rotate, a head assembly that performs read/writeoperations on the magnetic disk 24, and electronic circuitry that iscomposed of electronic components 70 are contained in a closed spacewithin the above single housing 21.

Further, the above disk driving means 15 has a spindle motor 26 that islocated at the inner portion of the magnetic disk 24 so that themagnetic disk can rotate and a fixed shaft 25 of spindle that is fixedin a predetermined position within the housing 21 so as to support themagnetic disk 24 rotatably.

Furthermore, the above head assembly has at least one magnetic head 27that executes reproducing/recording operations corresponding toread/write operations of the information on either surface of the upperand lower surfaces of the magnetic disk 24, at least one arm 28 thatsupports the magnetic head 27, and an actuator 29 that forces the arm 28to rotate in either direction and the magnetic head 27 to move to thepredetermined track on the magnetic disk 24.

Further, in some other preferred embodiments, a head with a smallpressing load is utilized as the above magnetic head. For example, whenthe contact type magnetic head, disclosed in Japanese Unexamined PatentPublication (Kokai) No. 3-178017 is utilized as the magnetic head 27, anextremely small load of several tens of mg can be used. On the otherhand, in the flying type head as shown in FIGS. 4 to 7, it is possiblefor a head with a relatively small load of several hundreds of mg to beutilized. Further, by applying the negative pressure type head sliderand load/unload mechanism to the disk drive according to the presentinvention, the friction of the head, caused when a spindle motor startsup, can be substantially neglected. By virtue of such advantages, aspindle motor, that starts up with a relatively low power voltage, canbe realized.

Furthermore, the above electronic circuitry includes an interfacecircuit 39 that allows communication with an external host computer, aread/write circuit 36 that receives read signals from the head assemblyand provides write signals to the head assembly, a servo circuit that iscomprised of a positioning circuit 37 and an amplifying circuit (headIC) 35 to control the operations of the magnetic disk 24 and the headassembly, and a control circuit 38 that receives control signals S_(c)from the external host computer via the interface circuit 39 andprovides the control signals S_(c) to the read/write circuit 36 and theservo circuit. More specifically, the control signals S_(c) and addresssignals S_(a) are sent from the host computer to the interface circuit39 via the connector 42. Further, the control signals S_(c) are inputinto the control circuit 38, and status signals S_(s) indicating thecurrent status of the magnetic disk drive 20 are issued from the controlcircuit 38 to the interface circuit 39. Also, the interface circuit 39is coupled to the positioning circuit 37, which determines the positionof the magnetic head 27 on the magnetic disk 24 in accordance withinstructions from the host computer. Here, the information of the aboveposition read by the magnetic head 24 is sent back to the positioningcircuit 37 as position signals S_(p), via the amplifying circuit 35, sothat accurate positioning can be performed by means of servo control.Further, power is supplied to all the above circuits via the connector42, together with any other associated circuits.

Hereinafter, with regard to the various signals in the interface circuitin the present invention, some additional explanation will be given. Asthe specifications of the interface utilized for the connector 42, thefollowing specifications can be used; namely, SCSI (Small ComputerSystem Interface), IDE (or PC/AT) and PCMCIA-ATA(AT Attachment) whichwill become the standards of the industry in the near future. Amongthese interface specifications, with regard to SCSI and IDE, inparticular, their electrical specifications are different from theelectrical specifications of the IC memory card fabricated in accordancewith PCMCIA. Accordingly, it is impossible for a disk drive fabricatedin accordance with SCSI or IDE, and the above IC memory card to be usedin common. On the other hand, since PCMCIA-ATA provides an extendedfunction of PCMCIA PC Card Standard, a disk drive fabricated inaccordance with PCMCIA-ATA and a disk drive fabricated in accordancewith usual PCMIA can be inserted into the same slot of a host computer.Therefore, in preferred embodiments, the PCMCIA-ATA can be recommendedas the interfaces of choice.

Furthermore, a power supply voltage of preferably 3-3.3V, should beused. In conventional electronic circuits, power consumption can bereduced by operating the circuits at a relatively low voltage. An ICmemory operative at a lower voltage can be obtained due to the recentprogress in the design of electronic circuits. However, the decreasingof a voltage supplied to mechanical components does not always lead to areduction in power consumption. On the contrary, in such a case, theratio of power consumption of electronic circuits for driving themechanical components to power consumption of the mechanical componentsper se is likely to be rather increased. The main designs foreffectively decreasing applied voltage are as follows. First, a spindlemotor can be improved and therefore the start-up operation at a lowervoltage can be realized. Second, the diameter of bearing means can bemade smaller and therefore a load torque can be reduced. Third, a headwith a lower pressure load can be adopted and therefore a load torqueduring start-up operation can be reduced. Fourth, a housing made ofmetal including iron can be adopted and therefor shielding againstvarious electrical noises can be improved.

Furthermore, as shown in FIG. 6, a plurality of insertion guide portions50 are provided on predetermined portions of the respective sides havinglonger dimensions of the housing 21. The above insertion guide portions50 are intended to allow the housing 21 to be inserted into a slot of ahost computer so that the disk drive can be placed in an operativecondition, if the respective connectors of the host computer and diskdrive are connected with each other. These insertion guide portions 50are constructed to have a thickness of less than the whole thickness ofthe housing 21.

As apparent from FIG. 7, the disk 24 is located approximately in thecentral position in respect to the thickness direction of the housing21. Accordingly, there exists a flat space 30 between the disk 24 andthe base 22, and another flat space 31 between the disk 24 and the cover23.

In the vicinity of the arm 28 in the space 30, an IC 35a isincorporated, that constitutes a first stage amplifying circuit 35 foramplifying very small read signals reproduced by the magnetic head 27.Further, in the space 30, ICs for processing analog signals, e.g., an IC36a that constitutes a part of the read/write circuit 36 and an IC 37athat constitutes a part of the positioning circuit 37, are alsoincorporated.

On the other hand, in a space 31 that is positioned on the opposite sideof the space 30 with respect to the disk 24 and is separated from thespace 30 by the disk 24, ICs for processing digital signals, e.g., an IC36b that constitutes the remaining part of the read/write circuit 36, anIC 36b that constitutes the remaining part of the positioning circuits37, an IC 38a that constitutes the control circuit 38 and an IC 39a thatconstitutes the interface circuit 38 are incorporated.

All the electronic components 70 that include the above-mentioned ICs36a-39a are assembled on the respective surfaces of a first body portion40a and a second body portion 40b of a printed circuit board 14, whichare attached close to the inner wall surfaces of the base 22 and cover23, respectively, and the above electronic components 70 are containedwithin the housing 21, together with the printed circuit board 14.Preferably, the above printed circuit board (PCB) 14 is a flexibleprinted circuit board (FPC) 40 that is bent into the lower first bodyportion 40a and the upper second body portion 40b. In this case, theabove flexible printed circuit board 40 has two bands of connectingportions 40c, 40d by which the lower first body portion 40a and theupper second body portion 40b are coupled with each other. Hereinafterthe reason why the longer side of the housing 21 is selected as the bentportions (the connecting portions) of the FPC40 in which the upper andlower portions thereof are integrated with each other, will be explainedin detail. As illustrated in FIGS. 4 and 6, FPC circuit patterns at theupper and lower sides are connected on the FPC. The signals flow fromthe magnetic head through the connector, via the head IC, demodulationcircuit (analog) in the read/write circuit and digital processingcircuit. As described above, in view of the analog circuit portion anddigital circuit portion being separated between the lower side and upperside of the FPC., respectively, the signals output from the demodulationcircuit and the control signals are arranged to pass through theconnecting portions. As the position where these connecting portions arelocated, both the shorter sides and longer sides of the housing may beselected. Also as described above, the connector is attached to one ofthe shorter sides, while the head actuator is located in the vicinity ofone of the shorter sides. Accordingly, if the upper and lower sides ofthe FPC are connected with each other in the shorter side, they must beconnected at the side of the head actuator. Such a connecting structureis disadvantageous in that the overall path for the signals becomeslonger. On the contrary, if the upper and lower sides of the FPC areconnected with each other in the longer side, the above-mentioned signalflow can be realized without any difficulties in arranging circuitpatterns. However, when a disk with a diameter of 4.8 cm (1.87 inches)is incorporated inside a housing of memory card size, the disk is likelyto protrude outside the housing and strike the longer sides of thehousing. To avoid this problem, a part of the connecting portions wherethe disk protrudes outside the housing is cut out. In such aconstruction, the connecting portions can be reasonably located at thelonger side of the housing. In this case, it is advantageous that theconnecting portions are separated into two parts as shown in FIG. 6, sothat the elastic force that is generated in the connecting portions whenthe FPC is bent back, can be reduced.

As illustrated in FIG. 8, the above connecting portions 40c (40d) arelocated across the base 22 and cover 23. Further, when the housing 21 isin a closed condition such that the cover 23 covers over the base 22,the connecting portions 40c (40d) are curved so that they protrudeinside the housing 21 as shown in FIG. 9. As apparent from FIG. 9, sincethe connecting portions are constructed to have excess length, itbecomes possible for the base 22 and cover 23 to be arranged in planedirections and for the various components to be incorporated inside thehousing 21. As the excess length of the connecting portions becomeslarge, the components can be incorporated more easily, while theprotruding parts formed by this excess length are likely to interferewith the disk 24 and the other mounted components. To avoid thisdifficulty, it is proposed that these protruding parts be bent backfurther so that they are folded together in multiple layers. Moreconcretely, in the condition that the base 22 and cover 23 are arrangedin plane directions, such a folded structure can be realized by forcingdown the center of the bridge portion of the FPC40 with a wire. In thecondition that the base 22 is overlaid with the cover 23, the cover 23adheres closely to the base 22 via a packing 41, and therefore the wholespace within the housing 21 where the disk, etc., are contained isclosed up tightly. In this case, to reduce the pressure differencebetween the inside and outside of the housing caused by the temperaturerise during operation of the disk drive, an air filter for circulationis attached to the housing. In that sense, it cannot always be said thatthe space within the housing is perfectly closed up. However, dust inthe air can be prevented from entering the housing. Therefore, thestructure, in which the air filter is provided, is also usually referredto as a tightly closed structure.

Further, the connector 42 is attached to either one of two sides havingshorter dimensions of the housing 21. Here, the above connector 42 islocated in a position opposite to the actuator 29 across the disk 24 andis located in the approximately central position in respect to thethickness direction of the housing 21, so that mechanical support of thewhole disk drive can be achieved by means of the connector 42 with goodbalance of weight.

The magnetic disk drive of the present invention does not incorporate avibration-free support mechanism that is employed in general devices,but employs a mechanical support using a connector which makes afeature.

The connector which has as many as 68 pins produces a considerably largeholding force but still consideration must be given to cope with thedisturbance. The disturbance which is internally generated stems from(1) vibration due to the unbalanced spindle and (2) seek reaction of theactuator. Furthermore, external vibration and shocks are added thereto.Here, first, countermeasure is taken against the above two causes ofinternal generation.

First, vibration due to the unbalanced spindle generates while thespindle is revolving and becomes a cause of error in position.Therefore, attention is given in an effort to minimize the amount ofresidual imbalance, and support conditions are contrived too to reducethe effect. Generally speaking, the vibration due to imbalance isdetermined by a moment of the center of rotation of the spindle and thecenter of gravity or the distance of the fulcrum. In the presentinvention which accomplishes the support using the connector, therefore,the spindle is disposed on a side close to the connector and theactuator is disposed on a side remote from the connector. The momentthat is generated can be decreased by about 40% compared with that ofthe constitution fabricated in an opposite manner, and the error inposition due to the vibration of imbalance can be decreased by 40%. Whencompletely balanced, only the moment of rotation is generated which doesnot change irrespective of the position of the actuator. In principle,therefore, there arises no adverse effect even when the actuator isdisposed on the side remote from the connector.

To cope with the reaction of the actuator, first, the connectoraccomplishes the linear support; i.e., considerably rigid support isaccomplished in the direction of rotation to suppress the rotary motionof the whole drive caused by the moment generated by the actuatorthereby to suppress the error in position caused by the turn of thedrive. The connector is disposed at the center in the thicknessdirection of the drive and, further, the center of gravity of theactuator is brought into this position, so that there takes place nomotion due to the seek reaction (moment) in the up-and-down direction orin the twisting direction. This makes it possible to suppress error inposition, fluctuation of floatation, etc. caused by the motion in thedirections outside the planes.

More concretely, the connector 42 is fixed on the cover 23 of thehousing 21 and is connected to the second body portion 40b of the FPC40, on which the digital electronic components such as the IC 39a of theinterface circuit 39 are assembled. Further, a part of the second bodyportion 40b, that is connected to the connector 42, is covered with thepacking 41.

A similar construction of the above-mentioned disk drive has beendisclosed in Japanese Unexamined Patent Publication (Kokai) No.60-242568. However, in such a known construction, it is not describedclearly that all the electronic components including analog and digitalcomponents are incorporated within a single housing, unlike the abovefirst preferred embodiment.

On the contrary, the disk drive having the construction according to thepresent invention as illustrated in the first preferred embodiment isintended to accommodate all the electronic components, as well as thedisk and various mechanical components by utilizing the spaces within asingle housing effectively. Consequently, the disk drive 20 can have asingle housing structure and can have a thickness dimension ofapproximately 5 mm which is the same as that of an IC memory card of theabove-mentioned type II PCMCIA. Therefore, the disk drive 20 becomesthinner and more compact than any disk drive according to a prior art,and it can be more easily used for a portable computer than the priorart disk drive.

Furthermore, since the connecting portions 40c, 40d are previouslyformed in the above-mentioned FPC 40, it becomes unnecessary to providea connector component for connecting two body portions 40a, 40b to eachother. Owing to the above advantage, the disk drive 20 can have an eventhinner dimension as desired for a suitable and portable memory device.

As described above, the construction of the disk drive in the firstpreferred embodiment has also the following features.

First, an analog circuit portion for processing analog signals and adigital circuit portion for processing digital signals are separatedfrom each other at the lower side and upper side of the housing,respectively.

Second, a substrate of the disk, that is generally made of metalincluding aluminum, is located between the above two separated circuitportions; namely, the disk substrate has a function ofelectromagnetically shielding the above two circuit portions from eachother.

In such a construction, it becomes possible for analog signals in theanalog circuit portion to be prevented from suffering negative influencedue to electromagnetic waves generated by the digital circuit portion.In other words, the disk drive in the first preferred embodiment has astructure in which a counter measure against various electric noises cabbe taken without increasing the thickness dimension of the disk drive.In this case, it will be also possible in the future for the thicknessof the disk drive to be reduced to 3.3 mm which is the same as that ofthe type I PCMCIA IC memory card.

Further, since the structure of such a disk drive is resistant toelectric noises, a disk drive operative at a lower power supply voltagecan be realized and power consumption in the disk drive can be reduced.

FIG. 10 is a view showing a second preferred embodiment of a disk drivestructure according to the present invention. To be more specific, FIG.10 is a sectional front view showing the main part of a disk driverelating to the second preferred embodiment of the present invention.From now on, any component that is the same as a component mentionedbefore will be referred to using the same reference number.

In the second preferred embodiment shown in FIG. 10, metal based printedcircuit boards 91, 92 are utilized instead of the flexible printedcircuit board 40 in the first preferred embodiment described above. Asillustrated in FIG. 10, both of a base 22 and a cover 23 are made ofmetal including iron, and on the respective inner wall surfaces of thebase 22 and cover 23, the metal based printed circuit boards 91, 92 aredirectly formed, respectively. Further, ICs 35a-39b (in FIG. 10, only IC38a is shown) are directly assembled on the metal based printed circuitboards 91, 92.

According to the second preferred embodiment, it is unnecessary for theprinted circuit board to be adhered to the inner wall surfaces of thebase 22 and cover 23. Therefore, the above second preferred embodimenthas an advantage in that the sequences for assembling electroniccomponents become simpler than the assembling sequences in the firstpreferred embodiment.

FIG. 11 is a view showing a third preferred embodiment of a disk drivestructure according to the present invention. To be more specific, (A)of FIG. 11 is a simplified top view and (B) of FIG. 11 is a simplifiedfront view, showing the characteristics of the third preferredembodiment.

As illustrated in (A) and (B) of FIG. 11, a supplementary shieldingsheet 61 is provided in a form such that a surrounding region outsidethe disk 24 and inside the base 22 and cover 23 is covered with theabove supplementary shielding sheet 61. In this construction, the loweranalog circuit portion and the upper other digital circuit portionwithin the housing 21 as in FIG. 7 can be separated electromagneticallyfrom each other. The third preferred embodiment as shown in FIG. 11 canbe effectively applied in a case where the whole region where the analogand digital circuit portions within the housing 21 are located cannot becompletely covered with the disk 24 alone.

FIG. 12 is a view showing a fourth preferred embodiment of a disk drivestructure according to the present invention. To be more specific, (A)of FIG. 12 is a simplified top view and (B) of FIG. 12 is a simplifiedfront view, showing the characteristics of the fourth preferredembodiment.

As illustrated in (A) and (B) of FIG. 12, first and second shieldingwalls 71, 72 each having the form of a rib are formed rib are formedinside the base 22 and cover 23, respectively. The first shielding wall71 at the side of the base 22 is located between the IC 36a and IC 37a.This first shielding wall 71 serves to prevent a reproducing/recordingcircuit block and a positioning circuit block, both analog circuitportions, from interfering with each other. Further, the secondshielding wall 72 at the side of the cover 23 is located between the IC36b and IC 37b. This second shielding wall 72 serves to prevent areproducing/recording circuit block and a positioning circuit block,both digital circuit portions, from interfering with each other, similarto the first shielding wall 71. In other words, the above first andsecond shielding walls 71, 72 are constructed such that the analogcircuit portion and the digital circuit portion are partitioned amongindividual function blocks, respectively. In such a construction, it canbe ensured that electromagnetic shielding is performed more efficientlythan the shielding in the third preferred embodiment shown in FIG. 11.

FIG. 13 is a view showing a fifth preferred embodiment of a disk drivestructure according to the present invention. To be more specific, (A)of FIG. 13 is a simplified top view and (B) of FIG. 13 is a simplifiedfront view, showing the characteristics of the fifth preferredembodiment.

As illustrated in (A) and (B) of FIG. 13, first shielding wall parts 81and second shielding wall parts 82 each having the form of a ribprotrude toward the disk 24 inside the base 22 and cover 23,respectively. More concretely, the first and second shielding wall parts81, 82 are formed along the boundary of a region within which themagnetic head 27 moves. In such a construction, the magnetic disk 27 andthe IC 35a constituting the first stage amplifying circuit, that aremost likely to suffer influence due to various electric noises, can beprotected from electromagnetic waves generated by the other circuitportions.

FIG. 14 is a view showing a sixth preferred embodiment of a disk drivestructure according to the present invention. To be more specific, FIG.14 is a sectional front view showing the main part of a disk driverelating to the sixth preferred embodiment of the present invention.

In FIG. 14, the flexible printed circuit board 90 is preferably used asa printed circuit board 14 (FIG. 6). This flexible printed circuit board90 has a double structure in which circuit patterns 90b-1, 90b-2 areformed on one surface of a film substrate 90a, while overall earthpatterns 90c-1, 90c-2 are formed on the other surface of the filmsubstrate 90a excluding bent portions thereof. Further, the aboveflexible printed circuit board 90 is provided along the inner wall ofthe housing 21. In this case, the circuit patterns 90b-1, 90b-2 face theinner wall surfaces of the bases 22 and cover 23, respectively, whilethe overall earth patterns 90c-1, 90c-2 face the lower and uppersurfaces of the disk 24, respectively.

Further, in FIG. 14, ICs 36a, 37a are assembled on the circuit patterns90b-1 of the flexible printed circuit board 90, and are adhered closelyto the inner wall of the base 22. On the other hand, ICs 36b, 37b, 38aand 39a are assembled on the circuit patterns 90b-2 of the flexibleprinted circuit board 90, and are adhered closely to the inner wall ofthe cover 23. On the surface of the base 22 and cover 23, heat radiatingfins 22Ba, 23Ba are formed. Respectively, by virtue of the above heatradiating fins 22Ba, 23Ba, the heat generated by the ICs 36a-39a can beeffectively radiated through the base 22 and cover 23 to the outside ofthe housing 21.

Here, it is assumed that electromagnetic waves are generated from thecircuit pattern 90b-2 dealing with digital signals and are directedtoward the other circuit pattern 90b-1 dealing with analog signals. Inthe construction of the sixth preferred embodiment, the above circuitpattern 90b-1 can be effectively shielded from the electromagnetic wavesby means of the overall earth patterns 90c-1, 90c-2, as well as the disk24.

Further, a portion 90A of the flexible printed circuit board 90, that isplaced near the magnetic head 27, represents the portion on which an IC35a is assembled. In respect to the portion 90A, the circuit pattern90b-1 is formed on the surface opposite to the surface of the otherportion of circuit pattern 90b-1 by utilizing through holes 90d.Consequently, the IC 35a can be located in the vicinity of the magnetichead 27. In such a construction, the electrical path from the magnetichead 27 through the IC 35a becomes shorter, and therefore thereproducing signals (read signals) are less apt to suffer influence dueto external disturbances, such as electrical noises.

FIGS. 15, 16, 17, 18 and 19 are views showing a seventh preferredembodiment of a disk drive structure according to the present invention.To be more specific, FIG. 15 is a perspective view showing the inside ofa magnetic disk drive; FIG. 16 is an exploded perspective view showingthe construction of FIG. 15 in more detail; FIG. 17 is a sectional viewtaken along a line III--III of FIG. 15; FIG. 18 is an enlargedperspective view showing a portion of FIG. 16 enclosed within a circleA; and FIG. 19 is an enlarged perspective view in which a portion ofFIG. 15 enclosed within a circle B is see from the side shown by anarrow V.

In these figure, 40-1 denotes a first printed circuit board elementpreferably made of a flexible printed circuit board on which an IC 37a,etc., is assembled. The above first printed circuit board element 40-1is placed on the inner wall surface 2A-1 of a base 22 made of metal,adhering to the above inner wall surface 2A-1 thereof. In this case, thereference numerals of ICs other than IC 37a and IC 37b (referred tohereinafter) are omitted to simplify the explanation of FIGS. 15 to 19.

Further, the first printed circuit board element 40-1 has two tongueportions 21-3, 21-4 that are projected outward one side 21-1 of a pairof two longer sides 21-1, 21-2 positioned along the longer direction ofthe above first printed circuit board element 40-1, and has a portion21-5 that is projected outward from the other side 21-2 thereof.Furthermore, this first printed circuit board element 40-1 has a tongueportion 21-7 that is projected outward from one shorter side 21-6 of theabove first printed circuit board element 40-1. On the tongue portions21-3, 21-4, 21-5 and 21-7, a plurality of terminals 22-1, 22-2, 22-3 and22-4 are formed, respectively.

The base 22 includes a rib-shaped first fringe portion 2A-2 having arectangular frame form over the whole circumference of the above base22. Further, the above first fringe portion 2A-2 comprises a pair oflonger sides 2A-2-1, 2A-2-2 and a pair of shorter sides 2A-2-3, 2A-2-4.Preferably, the upper surface 2A-2a of this fringe portion 2A-2 has aflat face.

Further, as illustrated enlarged in FIG. 18 shallow recessed parts2A-2b, 2A-2c and 2A-2d are formed in the predetermined positions of thelonger sides 2A-2-1, 2A-2-2 on the upper flat surface 2A-2a of thefringe portion 2A-2, while another shallow recessed part 2A-2e is formedin the predetermined positions of one shorter side 2A-2-3 thereon.

Also in FIG. 18, the above tongue portions 21-3, 21-4, 21-5 and 21-7 areconstructed to rise up once along the first fringe portion 2A-2 andfurther to be bent outward from the first fringe portion 2A-2.Furthermore, the tongue portions 21-3, 21-4, 21-5 and 21-7 are projectedon the longer sides 2A-2-1, 2A-2-2, and the shorter side 2A-2-3 andfinally are contained in the shallow recessed parts 2A-2b, 2A-2c, 2A-2dand 2A-2e. The terminals 22-1-22-4, i.e., a first group of terminals,are located so that they are exposed on the upper surface 2A-2a of thefirst fringe portion 2A-2.

Further, in FIGS. 15 to 19, 40-2 denotes a second printed circuit boardelement preferably made of a flexible printed circuit board on which anIC 37b, etc., is assembled, similar to the second printed circuit boardelement 40-1. The above second printed circuit board element 40-2 isplaced on the inner wall surface 3A-1 of a cover 23 made of metal, andadhered to the above inner wall surface 3A-1 thereof.

Furthermore, the second printed circuit board element 40-2 has twotongue portions 20-3, 20-4 that are projected outward from one side 25-1of a pair of two longer sides 20-1, 20-2 positioned along the longerdirection of the above second printed circuit board element 40-1, andhas a portion 20-5 that is projected outward from the other side 20-2thereof. Furthermore, this second printed circuit board element 40-2 hasa tongue portion 20-7 that is projected outward from one shorter side20-6 of the above second printed circuit board element 40-2. On thetongue portions 20-3, 20-4, 20-5, and 20-7, a plurality of terminals23-1, 23-2, 23-3 and 23-4 are formed, respectively.

The cover 23 includes a rib-shaped second fringe portion 3A-2 having arectangular frame form over the whole circumference of the above cover23. Further, the above second fringe portion 3A-2 comprises a pair oflonger sides 3A-2-1, 3A-2-2 and a pair of shorter sides 3A-2-3, 3A-2-4.Preferably, the upper surface 3A-2a of this fringe portion 3A-2 has aflat face.

Further, similar to the construction relating to the first fringeportion 2A-2 described above, shallow recessed parts 3A-2b, 3A-2c and3A-2d are formed at predetermined positions of the longer sides 3A-2-1,3A-2-2 on the upper flat surface 3A-2a of the fringe portion 3A-2, whileanother shallow recessed part 3A-2e is formed at a predeterminedposition of one shorter side 3A-2-3 thereon.

The above tongue portions 20-3, 20-4, 20-5 and 20-7 are constructed torise up once along the second fringe portion 3A-2 and further to be bentoutward from the second fringe portion 3A-2. Furthermore, these tongueportions 20-3, 20-4, 20-5 and 20-7 are projected on the longer sides3A-2-1, 3A-2-2 and the shorter side 3A-2-3 and finally are contained inthe shallow recessed parts 3A-2b, 3A-2c, 3A-2d and 3A-2e. The terminals23-1-23-4, i.e., a second group of terminals are located such that theyare exposed on the upper surface 3A-2a of the second fringe portion3A-2.

Further, in this construction, a fixed shaft 25 of a spindle, a magneticdisk 24, at least one magnetic head 27, at least one arm 28, an actuator29 and the like are assembled inside the base 22, and then the cover 23is arranged in a predetermined position on the base 22 in such a mannerthat the base 22 is covered with the cover 23. Furthermore, the uppersurface 2A-2a of the first fringe portion 2A-2 and the upper surface3A-2b of the first fringe portion 3A-2 are fixed together over the wholecircumference by utilizing an anisotropic conductive adhesive 32.

In the condition that the cover 23 is combined with the base 22 asdescribed above, the second tongue portions 20-3, 20-4, 20-5 and 20-7 inthe cover 23 face the first tongue portions 21-3, 21-4, 21-5 and 21-7 inthe base 22, respectively, and the second group of terminals 23-1-23-4face the first group of terminals 22-1-22-4, respectively. Consequently,as illustrated in FIG. 17, the above second tongue portions 20-3, 20-4,20-5 and 20-7 are arranged so as to be contained in the shallow recessedparts 2A-2b, 2A-2c, 2A-2c and 2A-2d of the base 22, respectively, whilethe above first tongue portions 21-3, 21-4, 21-5 and 21-7 are arrangedto be contained in the shallow recessed parts 3A-2b, 3A-2c, 3A-2c and3A-2d of the cover 23, respectively. In such an arrangement, the secondtongue portions 20-3, 20-4, 20-5 and 20-7 and first tongue portions21-3, 21-4, 21-5 and 21-7 are firmly fastened together by means of theanisotropic conductive adhesive 32. Here, all the tongue portions 20-3,20-4, 20-5, 20-7, 21-3, 21-4, 21-5 and 21-7 can be held in therespectively corresponding shallow recessed parts 2A-2b, 3A-3b, etc.,and therefore the above tongue portions 20-3, 21-3, etc., have nodisadvantageous influence on the respective adhering surfaces of thecover 23 and base 22. Therefore, the first and second fringe portions2A-2, 3A-2 can be adhered to each other in such a manner that the firstfringe portion 2A-2 is substantially perfectly glued to the secondfringe portion 3A-2 over the whole circumference thereof.

Further, as illustrated in FIG. 19, the anisotropic conductive adhesive32 has electrically conductive characteristics in respect to thedirection of the Z-axis, i.e., in the direction where this anisotropicconductive adhesive 32 is pressed between two tongue portions, while itdoes not have any electrically conductive characteristics in respect tothe direction of the X-axis and Y-axis. Consequently, the terminal 23-1of the cover 23 and the corresponding terminal 22-1 of the base 22 canbe electrically connected to each other. Further, electrical connectionscan be performed between the other terminals 23-2, 23-3 and 23-4 of thecover 23 and the respectively corresponding terminals 22-2, 22-3 and22-4 of the base 22 in a similar manner.

In the seventh preferred embodiment described above, the wholecircumference of the fringe portions 2A-2, 3A-2 are coated with theanisotropic conductive adhesive 32. However, alternatively, it ispossible for only the respective tongue portions in the base 22 andcover 23 to be coated with the anisotropic conductive adhesive 32, or itis also possible for the fringe portions 2A-2, 3A-2 and the tongueportions to be partially coated with the anisotropic conductive adhesive32.

In this case, since the printed circuit board is separated into twodifferent elements respectively corresponding to the base 22 and cover23, the above base 22 and cover 23 can be treated independently.Therefore, the seventh preferred embodiment has an advantage in that theprocess for assembling the magnetic disk 24, the spindle 25, themagnetic head 27 and the like inside the housing 21 becomes relativelysimple. Further, since all the tongue portions are held in respectivelycorresponding shallow recessed parts, the base 22 and cover 23 can befixed together closely by means of the anisotropic conductive adhesive32 over the whole circumference. Therefore, the seventh preferredembodiment has another advantage in that a sufficiently closed conditionwithin the housing 21 can be ensured.

FIG. 20 is a view showing one example of a change in the enclosure partof tongue portions in the seventh preferred embodiment as illustrated inFIG. 17. In FIG. 20, the structure inside the housing 21 is illustratedmore briefly to simplify the explanation.

As shown in FIG. 20, at least one concave stepped part 33' is providedas the enclosure part of tongue portions only at the side of the cover23, unlike the construction of FIG. 17. Further, in FIG. 20, therespective tongue portions 21-1, 20-1 in the base 22 and cover 23 arecontained in a space between the above recessed stepped part 33 and theupper surface 2A-2a of the fringe portion 2A-2 of base 22, in acondition such that the respective tongue portions 21-1, 20-1 in thebase 22 and cover 23 overlap each other.

FIG. 21 is a view showing another example of a change in the enclosurepart of tongue portions in the seventh preferred embodiment as in FIG.17. Also in FIG. 21, similar to FIG. 20, the structure inside thehousing 21 is illustrated more briefly to simplify the explanation.

As shown in FIG. 21, at least one convex part 34 is provided as theenclosure part of tongue portions in the fringe portion 3A-2 of thecover 23, unlike the construction of FIG. 17. Further, in FIG. 20, therespective tongue portions 21-1, 20-1 of the base 22 and cover 23 arecontained in a space between the above convex part 34 and the inner wallsurface 2A-1 of the base 22, in a condition such that the respectivetongue portions 21-1, 20-5 of the base 22 and cover 23 overlap eachother.

FIG. 22 is a view showing an eighth preferred embodiment of a disk drivestructure according to the present invention. In FIG. 22, the main partof the structure inside the housing 21 is illustrated.

As shown in FIG. 22, the base 22 and cover 23, that are made by pressforming a metal plate, have flange portions 2Ba, 3Ba in thecircumferences of the above base 22 and cover 23, respectively. Further,in FIG. 22, the respective tongue portions 21-3, 20-3 of the flexibleprinted circuit board elements 40-1, 40-2 are coated with theanisotropic conductive adhesive 32 and are held between the above twoflange portions 2Ba, 3Ba. Finally, the base 22 and cover 23 are fixedtogether by applying a pressure F on the flange portions 2Ba, 3Ba andadhering them to each other.

FIG. 23 is a view showing a ninth preferred embodiment of a disk drivestructure according to the present invention. Also in FIG. 23, similarto FIG. 22, the main part of the structure inside the housing 21 isillustrated.

As shown in FIG. 22, the base 22 and cover 23, that are made by pressforming a metal plate, have other flange portions 2Ca, 3Ca in thecircumferences of the above base 22 and cover 23, respectively. Here,the dimension of the overhang of one flange portion 2Ca is twice as longas that of the overhang of the other flange portion 3Ca. First, therespective tongue portions 21-3, 20-3 of the flexible printed circuitboard elements 40-1, 40-2 are coated with the anisotropic conductiveadhesive 32 and are held between the above two flange portions 2Ca, 3Ca.Next, the former flange portion 2Ca is folded back in such a manner thatit covers the latter flange portion 3Ca, and a bent portion 2Ca-1 isformed at the upper side of the flange portion 3Ca as illustrated inFIG. 23. Finally, the base 22 and cover 23 are adhered together byapplying a pressure F to the flange portion 2Ca and the bent portion2Ca-1 and by fitting the inner flange portion 3Ca into the outer flangeportion 2Ca. In this construction, fitting and adhering of the flangeportions are simultaneously performed, so the electronic components suchIC 37a, 37b can be tightly enclosed in the housing 21 with higherreliability.

FIGS. 24 and 25 are views showing a tenth preferred embodiment of a diskdrive structure according to the present invention. To be more specific,FIG. 24 is a schematic flat view showing the whole disk drive structureand FIG. 25 is a schematic sectional front view showing the structureinside the housing.

In these figures, similar to all the other previous embodiments, onemagnetic disk 24 preferably having a diameter of 48 mm or 1.89 inches, adisk driving means 15, a head assembly that includes magnetic heads 27,an actuator 29, etc., electronic circuitry and a printed circuit board14 such as a flexible printed circuit board are contained in a closedspace within a single housing 21, which is constituted by a base 22 andcover 23 and has the same dimensions as the outer dimensions of the typeII PCMCIA IC memory card. In FIGS. 24 and 25, the connector 42 isomitted.

Further, in the remaining space within the housing 21 other than amovable space where the magnetic disk 24, the disk driving means 15, thehead assembly and the other enclosed components as described above canbe moved, a filler 16 having a form corresponding to the concavity andconvexity of the remaining space is placed in the remaining space.Preferably, the above filler 16 is made of a resin material, such aspolycarbonate resin or epoxy resin.

In this construction, the unoccupied space can be reduced to the minimumdimensions required. Therefore, the deformation of the housing 21, thatmay occur by applying various external forces thereto, can be easilyprevented, and disadvantageous vibrations of the enclosed componentswithin the housing 21 can be also avoided.

FIG. 26 is a sectional view showing an eleventh preferred embodiment ofa disk drive structure according to the present invention. In FIG. 26,only the main part of the structure inside the housing 21 relating tothe characteristics of the eleventh preferred embodiment is illustrated.

The construction of the above eleventh preferred embodiment is similarto that of the tenth preferred embodiment described before. However, theconstruction of the eleventh embodiment is different from that of thetenth embodiment in the following points:

first, the printed circuit board 14 is divided into a lower printedcircuit board part 14a and an upper printed circuit board part 14b, thatare composed of flexible printed circuit board material or thinly-madeprinted circuit board material and that are laid separate from eachother on the inner wall surfaces of the base 22 and cover 23,respectively; and,

second, a magnetic material 16-1, that is fabricated by mixing anadhesive made of resin with a magnetic powder such as Mn--Zn ferrite, iscoated on the outer peripheral surface of the above-mentioned filler 16.

Also in the construction of the eleventh preferred embodiment, similarto that of the tenth preferred embodiment, the deformation of thehousing 21 can be firmly prevented by virtue of the filler 16. Here,both of the printed circuit board parts 14a, 14b are usually located inproximity to the magnetic head, and therefore electromagnetic noises arelikely to leak from these printed circuit board parts 14a, 14b.Consequently, such electromagnetic noises are superimposed onreproducing/recording signals (read/write signals) and thesignal-to-noise (S/N) ratio may be deteriorated. However, in theconstruction of the eleventh preferred embodiment, since the magneticmaterial 16-1 serves to electromagnetically shield the electromagneticnoises, deterioration of the signal-to-noise (S/N) ratio can be avoided.

FIG. 27 is a sectional view showing a twelfth preferred embodiment of adisk drive structure according to the present invention. Also in FIG.27, only the main part of the structure inside the housing 21 relatingto the characteristics of the twelfth preferred embodiment isillustrated.

The construction of the above twelfth preferred embodiment is similar tothat of the tenth and eleventh preferred embodiments described before.However, the construction of the twelfth embodiment is different fromthat of the other embodiments in that a conductive filler 16-2, which isformed by forcing a conductive material to be included in an insulatingfiller, such as polycarbonate resin or epoxy resin, is placed in theabove-mentioned space in the housing 21.

Also in the construction of the twelfth preferred embodiment, similar tothat of the eleventh preferred embodiment, the deformation of thehousing 21 can be firmly prevented by virtue of the conductive filler16-2. Further, in the construction of the twelfth preferred embodiment,since the conductive filler 16-2 also serves to electromagneticallyshield from electromagnetic noises, deterioration of the signal-to-noise(S/N) ratio can be avoided, similar to the eleventh preferredembodiment.

FIG. 28 is a sectional view showing a thirteenth preferred embodiment ofa disk drive structure according to the present invention. Also in FIG.28, the main part of the structure inside the housing 21 is illustrated.

In FIG. 28, an elastic adhering film 16-3 composed of an elasticadhesive including rubber, etc., is coated on the outermost peripheralsurface of the filler 16. Further, the filler 16 enclosed with anelastic adhering film 16-3 is placed in the above-mentioned space in thehousing 21. In this construction, the above filler 16 fits snugly withthe base 22, cover 23 and each of the enclosed components within thehousing 21 by virtue the elastic adhering film 16-3. Therefore, thethirteenth preferred embodiment has an advantage that the vibrations ofthe above filler 16, which are likely to be generated during operationof the disk drive, can be surely prevented.

FIG. 29 is a sectional view showing a fourteenth preferred embodiment ofa disk drive structure according to the present invention. Also in FIG.29, the main part of the structure inside the housing 21 is illustrated.

In FIG. 29, at least one signaling lead wire 14-1 is embedded in afiller 16, corresponding to the predetermined positions of the lower andupper printed circuit board parts 14a, 14b as described in FIG. 26.Further, the above filler 16 is placed in the above-mentioned space,similar to the thirteenth preferred embodiment, etc. In thisconstruction, similar to the tenth preferred embodiment as illustratedin FIG. 25, the deformation of the housing 21, that may occur byapplying various external forces thereto, can be easily prevented.Moreover, the wiring connection further necessitated in the lowerprinted circuit board part 14a or in the upper printed circuit boardpart 14b individually and the wiring connection between the lower andupper printed circuit board parts 14a, 14b can be realizedsimultaneously.

FIGS. 30, 31, 32, 33 and 34 are views showing a fifteenth preferredembodiment of a disk drive structure according to the present invention.To be more specific, FIG. 30 is a schematic exploded perspective viewshowing an essential construction; FIG. 31 is a schematic enlargedsectional view showing an essential construction; FIG. 32 is an explodedperspective view showing a disk drive structure in more detail; FIG. 33is a perspective view showing the inside of a disk drive; and FIG. 34 isan enlarged sectional view showing the main part of a disk drive in moredetail.

In the fifteenth preferred embodiment, as illustrated in these figures,a disk drive 20 comprises a single thin rectangular housing 21 that isconstituted by a base 22 and a cover 23 and that has outer dimensions ofapproximately 85.6 mm×54 mm×5 mm which are the same as an IC memory cardof type II of PCMCIA, similar to the other embodiments described before.More concretely, each of the above base 22 and cover 23 are fabricatedby forming a metal plate with a height of 4 to 5 mm by means of drawinginto a form of a vessel. Typically, a height of the base 22 is 2 mm,while a thickness of the cover 23 is 3 mm. The steel plate with thethickness of 0.4-0.5 mm is formed by means of drawing and the base 22and cover 23 each having an opening in one side and each having a vesselform. Accordingly, if this base 22 and cover 23 are combined together,the total thickness, i.e., a thickness dimension of the rectangularhousing 21, becomes 5 mm.

Hereinafter, the reason why the height of the base 22 is designed to bedifferent from the height of the cover 23 will be explained in detail.As described above, according to the specification of type II of PCMCIA,both the longer sides of the housing serve as the insertion guideportion to the host computer, and therefore the related longer sides arelimited to 3.3 mm in length. Since this portion touches with the outerperipheral of the disk having a diameter of 1.89 inch, i.e., 48 mm, itis preferable to dispose the disk at the center of the width of thehousing. Further, in correspondence with the above arrangement of thedisk, it is required to form a gun barrel shaped recess such as shown inFIG. 48 to each of the base and cover. Such complicated drawing reducesthe area of a flange surface and also strength of both the base and thecover and coupling intensity therebetween. In order to avoid this, theheight of the base is shifted with respect to that of the cover, andthus thinner one of the flange surfaces can be surely obtained. Notethat it is also preferable to dispose the disk at the center of thewidth of the housing, since the electronic parts, mounted on the innerwalls of the base and the cover, have the same maximum height at thebase side and the cover side.

Further, in one of the shorter sides of the rectangular housing 21, aspace for fixing a connector 42 is provided. In the other shorter sideand two longer sides of the housing 21, as illustrated in FIG. 34,coupling flanges 12-1, 12-2, extend outward at the outer peripheralportion of the above base 22 and cover 23, respectively, in accordancewith the characteristics of the fifteenth preferred embodiment.

The rectangular housing 21 includes at least one magnetic disk 24, aspindle motor 26, at least one magnetic head 27, at least one arm 28, anactuator 29, electronic components 70 and the like, similar to theembodiments described before, e.g., the first preferred embodiment shownin FIGS. 3 to 9. Here, the actuator 29 comprises a magnet portion 29acomposed of at least one permanent magnet, a yoke portion 29c located insuch a manner that it encloses the permanent magnet, and a movable coilportion 29b located inside the yoke portion 29c. In this case, thedetailed explanation of the above disk drive structure other than theportion of the coupling flanges 12-1, 12-2 is omitted to clarify thecharacteristics of the fifteenth preferred embodiment.

As typically shown in FIG. 32, the base 22 is combined with the cover 23by overlapping the respectively corresponding coupling flanges 12-1,12-2 of the base 22 and cover 23 with each other. Further, the couplingflanges 12-1, 12-2 are preferably jointed and fastened together by spotwelding, if both of the base 22 and cover 23 are made of metal includingiron. Alternatively, hermetic sealing to some extent can be guaranteedif the seam-welding is effected in which spot welding is continuouslycarried out. When the base and the cover are made of a metal other thaniron or a resin material, the coupling flanges are joined together bysuch means as wrap-seaming, screws or riveting. Metal including iron canbe joined together by such means, as a matter of course. Alternatively,if both of the base 22 and cover 23 are made of metal including aluminumor made of a resin material, these coupling flanges 12-1, 12-2 arepreferably jointed and fastened together by screws or rivets. Further,in the outer peripheral portion of the above jointed coupling flanges12-1, 12-2, a frame 13 composed of a pair of L-shaped frame elements13a, 13b is attached to force the jointed coupling flanges 12-1, 12-2 tobe closed up tightly. Each of these L-shaped frame elements 13a, 13b aremade of so-called engineering plastic, e.g., polyamide resin orpolyphenylenesulfide resin and have a sectional form having a recesscorresponding to the outer shape of the jointed coupling flanges 12-1,12-2, as illustrated in FIG. 34. In this case, the L-shaped frameelements 13a, 13b are fixed to the jointed coupling flanges 12-1, 12-2of the housing 21 by adhesion utilizing adhesive or by welding the frameelements 13a, 13b per se, and serve as a sealing means so that it can beensured that the inside of the housing 21 remains in a closed condition.

In this construction, the mechanical strength and the condition oftightness of the housing 21, whose coupling flanges 12-1, 12-2 arefastened together as described above, can be improved remarkably.Further, since each of the L-shaped frame elements 13a, 13b serves as abuffer means that absorbs the mechanical shock caused by externalfactors such as a fall of the disk drive 20, deformation, damage or thelike to the housing 21 can be prevented.

Furthermore, since the disk drive 20 is the same size as an IC memorycard, it may become possible for the disk drive 20 to be compatible withthe currently used IC memory cards and to be connected to an externaldevice, e.g., a host computer. In this case, each of the L-shaped frameelements 13a, 13b serves as an insertion guide rail that guides thehousing 21 of the disk drive 20 toward the host computer so that thehousing 21 can be easily inserted into the host computer.

FIG. 35 is a sectional view showing a sixteenth preferred embodiment ofa disk drive structure according to the present invention. In FIG. 35,only the main part of the structure inside the housing 21 relating tothe characteristics of the sixteenth preferred embodiment isillustrated.

The construction of the above sixteenth preferred embodiment is similarto that of the fifteenth preferred embodiment described before. However,the construction of the sixteenth embodiment is different from that ofthe other embodiments in that the frame 13 is composed of metal frameelements 33a, 33b, instead of the frame elements 13a, 13b of resinmaterial. In this case, each of the above metal frame elements 33a, 33bis directly fitted with the jointed coupling flanges 12-1, 12-2 of thehousing 21 and is finally fixed to the jointed coupling flanges 12-1,12-2 applying predetermined pressure to the metal frame elements 33a,33b.

In this construction, the process of adhering the frame 13 to thecoupling flanges 12-1, 12-2 as in the fifteenth preferred embodimentbecomes unnecessary. Therefore, the sequences for fixing the frame 13can be more simplified as a whole and the cost of fabrication of thedisk drive can be reduced.

FIG. 36 is a sectional view showing a seventeenth preferred embodimentof a disk drive structure according to the present invention. Also inFIG. 36, only the main part of the structure inside the housing 21relating to the characteristics of the seventeenth preferred embodimentis illustrated.

The construction of the above seventeenth preferred embodiment issimilar to that of the fifteenth preferred embodiment described before.However, the construction of the seventeenth embodiment is differentfrom that of the other embodiment in that the frame 13 has a doublestructure such that rubber frame elements 34a, 34b each having a recessare overlaid with metal frame elements 33a, 33b, respectively. In thiscase, first, each of the rubber frame elements 34a, 34b is fixed to thejointed coupling flanges 12-1, 12-2 by means of an adhesive includinggum, etc. Next, the metal frame elements 33a, 33b are directly fittedwith the rubber frame elements 34a, 34b, respectively. Finally, theabove metal frame elements 33a, 33b are firmly fixed to the rubber frameelements 34a, 34b and the coupling flanges 12-1, 12-2 by applyingpredetermined pressure to the metal frame elements 33a, 33b.

In the construction of the seventeenth embodiment, it is necessary fortwo kinds of frame elements to be fixed separately due to the doublestructure of the frame, and therefore the sequences of fixing the frameare more involved than those of fixing the frame in the fifteenth andsixth preferred embodiments. However, the above seventeenth embodimenthas an advantage in that the degree of tightness in the jointed couplingflanges 12-1, 12-2 can become higher than the fifteenth and sixthpreferred embodiments and further mechanical shock caused by a fall ofthe disk drive can be absorbed more effectively than the above-mentionedembodiments by virtue of the rubber frame elements 34a, 34b.

Furthermore, in this case, it is also possible for the rubber frameelements 34a, 34b and the metal frame elements 33a, 33b to be combinedinto a unified form in advance. In this manner, the unified form can beeasily attached to the outer peripheral portion of the jointed couplingflanges 12-1, 12-2.

FIG. 37 is a sectional view showing an eighteenth preferred embodimentof a disk drive structure according to the present invention. Also inFIG. 37, only the main part of the structure inside the housing 21relating to the characteristics of the eighteenth preferred embodimentis illustrated.

The construction of the above eighteenth preferred embodiment is similarto that of the seventeenth preferred embodiment described before.However, the construction of the eighteenth embodiment is different fromthat of the seventeenth embodiment in that the respective recesses ofthe metal frame elements 33a, 33b of the former embodiment are formed tobecome relatively deep and that the respective bottom parts of the abovemetal frame elements 33a, 33b are previously filled with rubber elements34c, 34d. In this construction, the metal frame elements 33a, 33b arefitted with the jointed coupling flanges 12-1, 12-2 and firmly fixedthereto by pressing, in a form such that the rubber elements 34c, 34dcontact the outer side portion of the jointed coupling flanges 12-1,12-2. The eighteenth embodiment has the same advantage as theseventeenth embodiment described before.

FIG. 38 is a view showing another example of a frame applied to a diskdrive according to the present invention as illustrated in FIG. 32. Inthe fifteenth to eighteenth embodiments described above, examplesutilizing a pair of L-shaped frame elements were illustrated in allcases. However, as shown in FIG. 38, it is also possible for a singleunified U-shaped frame 33 to be utilized instead of the L-shaped frameelements. Though not diagramed, furthermore, the base and the cover maybe joined together by using the frame only or by using the frame and theadhesive agent in combination without relying upon the welding,wrap-seaming, screws or riveting explained with reference to FIG. 32.

In all the embodiments relating to a disk drive structure according tothe present invention as described above, preferably, at least onereinforcing stud in the thickness direction of the base 22 and cover 23is provided inside the housing 21, since the clearance between the base22 and cover 23 inside the housing 21 is so small that deformation ofthe housing 21 may occur when extremely large external forces areapplied. By virtue of the above reinforcing stud, the mechanicalstrength of the housing 21 in respect to the thickness direction thereofcan be sufficiently ensured even against extremely large externalforces.

Further, in each case of the above-mentioned embodiments relating to adisk drive structure, an example in which the present invention isapplied to a magnetic disk drive has been illustrated. However, itshould be noted that the present invention can be also applied to amagneto-optical disk drive and an optical disk drive. Naturally, amagneto-optical disk drive and an optical disk drive can be utilizedinstead of a magnetic disk drive in all the embodiments describedhereinafter.

The structure of the spindle of the magnetic disk drive according to thepresent invention will now be described with reference to FIGS. 39 and40. The structure of a portion including bearing means of the headactuator is essentially the same as the structure described below, andis not mentioned here.

As mentioned earlier, the magnetic disk drive of the present inventionhas a thickness which is as small as less than 5 mm, and in which thebase 22 and the cover 23 constituting the housing are made of a thinplate or, preferably, a steel plate formed by press having a thicknessof 0.4 to 0.5 mm. Therefore, the magnetic disk drive is essentially weakagainst the external force in the direction of thickness thereof. Inorder to reinforce the strength, therefore, it has been attempted toerect studs between the base and the cover as mentioned earlier.However, it is not allowed to effect such a reinforcement in the portionwhere the disk 24 exists or in the portion where the actuator moves.Preferably, therefore, a structure is put into practice which has afixed shaft 18 and in which the center shaft of the spindle and thecenter shaft of the actuator are of the type of outer wheel rotationthat plays the role of the above-mentioned stud.

FIG. 42 is a diagram illustrating the structure of a preferred spindleof the present invention. The magnetic disk 24 is held by the spindlehub 11 which is supported by the fixed shaft 18 via bearing means 26-2.The fixed shaft 18 is fixed to the base 22 by caulking. In addition tothe caulking, the fixed shaft may be fastened to the base by welding,forced fitting, adhesion or by using a screw as will be described later.On the other hand, the spindle motor 26 has a rotor magnet 26-3 fittedto the recessed portion in the spindle hub 11 and has a stator coil 26-4fastened to the base 22 and opposed to the rotor magnet 26-3, androtates the magnetic disk.

First, the structure of the fixed shaft 18 shown in FIG. 42 will bedescribed in detail with reference to FIG. 28 and FIG. 49. Referring toFIG. 49, the fixed shaft 18 is constituted by a portion for mounting thebearing, a lower thin flange portion 18e, and a further lower caulkingportion 18f. The caulking portion 18f is inserted in a predeterminedhole in the base 22, and is fastened to the base 22 by cold caulking orhot caulking.

The flange portion 18e of the fixed shaft 18 exhibits two functions asdescribed below. A first function is that the fixed shaft is erectedperpendicularly to the surface of the base maintaining good precisionowing to the presence of the flange. A second function is that it servesas a reference plane for the bearing means. In the magnetic disk driveof the present invention, the distance between a pair of bearings in thebearing means 26-2 becomes very short since the housing has thethickness of smaller than 5 mm. The tilt precision of the magnetic diskcan be improved by increasing the distance between the upper bearing andthe lower bearing. In the disk drive of the present invention however,the upper bearing and the lower bearing are almost in contact with eachother as shown in FIG. 42 and a sufficient distance is not maintained.In the present invention, therefore, the lower end surface of the innerwheel of the bearing is abutted to the upper surface of the flange 18ethat serves as a dimensional reference of the fixed shaft 18 in order tomaintain good tilt precision. In order to favorably realize this, it isdesired that the outer diameter of the flange portion is as great aspossible. In this embodiment, the outer diameter of the flange is set tobe nearly equal to or greater than an average distance between the pairof bearings of the bearing means 26-2.

The coupling means between the fixed shaft 18 and the cover 23 will bedescribed later.

FIG. 43 is a diagram which illustrates the pre-load of the bearing meansof FIG. 42. In this case, the first and second bearing means can havesubstantially the same structure.

Being limited by the thickness of the housing as described above, thedistance between the pair of bearings of the bearing means is very shortand a sufficiently large rigidity against the moment is not obtained. Asshown in FIG. 43, therefore, a pre-load means such as a spring 26b isprovided between the upper outer wheel and the lower outer wheel of thebearing means in order to give a predetermined load in the axialdirection. Here, the two exterpolation lines link the points at which aroller 26a comes in contact with the outer wheel and the inner wheel.The distance D between the two intersecting points at which the twoexterpolation lines intersect the center of revolution of the spindlecan be increased to be longer than the average distance S between thepair of bearings of the bearing means by using the pre-load employed inthe embodiment. In FIG. 43, the distance is about twice as great as theaverage distance S and, hence, the rigidity against the moment which isabout twice as great is obtained.

Next, a preferred embodiment of the bearing means will be described inconjunction with FIG. 42. This embodiment uses a unitary shaft-typebearing in which the upper and lower inner wheels are formed as aunitary structure. Such a bearing constitution makes it possible toobtain more improved precision than that of the combination of theconventional bearings which have been split into upper and lower sides.Further, the bearing means can be mounted on the fixed shaft 18 bysimply fitting and adhering the hollow hole (inner circle) of theintegrally formed inner wheel onto the fixed shaft. Therefore, thebearing means can be fitted to the fixed shaft 18 separately fromfitting the means that gives the pre-load.

As shown in FIG. 50, furthermore, it is allowable to directly fasten theshaft to the base without forming a hollow hole that is shown in FIG. 42in the shaft that corresponds to the inner wheel of the unitaryshaft-type bearing. This method, however, involves the followingproblem. First, the part constituting the bearing requires a high degreeof machining precision for which it is difficult to effect suchmachining as flanging. Second, the bearing material has such a highhardness that inhibits assembling that involves plastic deformation suchas caulking. In this case, therefore, means is employed such asfastening by using a screw or slightly forced fitting which, however, isnot capable of offering a high degree of fastening strength.

Described below with reference to FIG. 42 are methods of fastening thefixed shaft 18 to the base 22 by welding. FIG. 42 is a diagram forexplaining the fastening by caulking, but to which reference is alsomade here for explaining the welding since it has quite the sameappearance.

According to a first method, the lower end of the fixed shaft 18inserted in a through hole of the base 22 is fastened to the inner edgeof the through hole by laser spot welding.

According to a second method, a portion that corresponds to the flangeof the fixed shaft around the through hole is fastened from the lowersurface of the base by laser spot welding.

According to a third method, no through hole is formed in the base 22,no base insertion portion is formed in the fixed shaft 18, and the lowersurface of the flange, i.e., the lower end surface of the fixed shaft 18is fastened from the lower surface of the base by spot welding.

The above-mentioned methods of fastening the base 22 and the fixed shaft18 together by welding can be replaced by the method of fastening usingan adhesive. In this case, however, the bonding strength by adhesion isinferior to that of welding, as a matter of course.

Described below is another embodiment of the method of fastening thefixed shaft which is different from the methods shown in FIG. 42.

FIG. 39 is a diagram illustrating a second embodiment of the structureof the fixed shaft in the magnetic disk drive of the present invention.In this embodiment, a substantial fixed shaft is a hollow shaftdesignated at 20-1 which is fitted and adhered to a pin 15-1 that isfastened by caulking to the base 22, and is thus erected on the base 22.A second pin 15-2 which forms a pair together with the first pin 15-1has the same diameter as the first pin 15-1 and further has a flangeportion. The second pin 15-2 is inserted in a stepped hole of the cover23 from the outer surface side of the cover 23, and is bonded to thefixed shaft 26-1 using an adhesive agent. The second pin 15-2 is furtherfastened to the cover 23 by adhesion or spot welding. In FIG. 39 unlikein FIG. 42, the bearing means is not the unitary shaft-type bearing butconsists of a pair of bearings 26-2 having separate inner wheels andwhich are fastened by adhesion to the fixed shaft 26-1.

FIG. 40 is a diagram illustrating a third preferred embodiment of thestructure of the fixed shaft in the magnetic disk drive of the presentinvention. Like FIG. 39, FIG. 40 representatively illustrates in crosssection and on an enlarged scale the structure of the fixed shaft in thespindle motor 26.

What makes the structure of this third preferred embodiment differentfrom the second embodiment is that a pin 15-3 of a shape shown is usedinstead of two pins 15-1 and 15-2, and the pin 15-3 is fastened bywelding to the base 22 and is further fastened to the cover 23 in aplastically deformed manner.

Concretely speaking, the pin 15-3 is passed through the stepped hole ofthe base 22 in a first stage. In a next stage, the flange portion of thepin 15-3 is fastened to the stepped bottom surface of the base byelectric spot welding or by laser spot welding. Moreover, the fixedshaft 20-1 to which the bearing means 26-2 is adhered is inserted andadhered in the pin 15-3. In the final stage, the pin 15-3 is fitted inthe stepped hole of the cover 23, and the head of the pin 15-3 iscrushed by the plastic working so as to be fastened to the cover 23.

FIG. 41 is a diagram which illustrates a fourth preferred embodiment ofthe structure of the fixed shaft in the magnetic disk drive of thepresent invention. Like FIG. 39, FIG. 41 representatively illustrates incross section and on an enlarged scale the structure of the fixed shaftin the spindle motor 26.

What makes the structure of this fourth favorable embodiment differentfrom the third embodiment is that the bearing means has an inner wheeland an outer wheel that are constituted as a unitary structure. In thisbearing constitution, not only the inner wheel but also the outer wheelare formed as a unitary structure making a difference from the unitaryshaft-type bearing structure shown in FIG. 42. That is, in thisembodiment, a pre-load is exerted in the step of fabricating the innerwheel, balls and outer wheel. Accordingly, no pre-load or no precisioncontrol is required in the step of assembling the magnetic disk drive,and the rotational precision of the spindle is improved.

FIG. 44 is a diagram illustrating a fifth preferred embodiment or thestructure of the fixed shaft in the magnetic disk drive of the presentinvention. This embodiment is different from the first to fourthembodiments with respect to that the fixed shaft 18 is fastened to thebase 22 by using a screw 43 and that the bearing means 26-2 which is notof the unitary shaft-type is directly adhered to the fixed shaft 18which is not hollow but is solid.

Described below is the structure of fastening the fixed shaft 18 to thecover 23.

FIG. 45 is a diagram showing the internal structure of the housing ofwhen the cover 23 is removed, i.e., showing the end of the spindle 18and the end of the actuator shaft 45.

FIG. 46 is a diagram illustrating a preferred embodiment for fasteningthe fixed shaft 18 in the magnetic disk drive of the present inventionshown in FIG. 42 to the cover 23. In FIG. 46, the coupling portionbetween the fixed shaft 18 and the base 22 is different from that ofFIG. 42, but the coupling to the cover 23 is the same, and there will beno problem in the description. Moreover, the coupling between theactuator shaft 45 and the cover 23 is the same and is not describedagain, here.

A stepped portion 18c is formed at the upper part of the fixed shaft 18,and a small-diameter portion 18d having a diameter D smaller than thediameter D of the fixed shaft 18 is formed at an upper part of thestepped portion 18c so as to protrude from the end of the fixed shaft18.

Moreover, a length T₁ from the bottom surface 18a of the fixed shaft 18(from the lower surface of flange 18f in FIG. 42) to the stepped portion18c is slightly greater (by about 0.02 to 0.06 mm in this embodiment)than a distance L₂ from the upper surface 22b of the base 22 to thelower surface of the cover 23. Further, a through hole 23b has beenformed in a portion of the cover 23 that faces the insertion hole 22cformed in the base 22. In this embodiment, the inner diameter D₁ of thethrough hole 23b is smaller than the outer diameter D of the fixed shaft18, but is greater than the diameter d of the small-diameter portion 18dat the end of the fixed shaft (D>D₁ >d). When the cover 23 is mounted onthe base 22, therefore, the small-diameter portion 18d of the fixedshaft 18 is inserted in the through hole 23b of the cover 23.

From now on, various embodiments of a fixed shaft construction of a diskdrive according to the present invention will be described withreference to FIG. 39 to FIG. 49.

FIG. 39 is a view showing a first preferred embodiment of a fixed shaftconstruction of a disk drive according to the present invention. In FIG.39, an enlarged schematic sectional view of a fixed shaft constructionin a spindle motor 26 is illustrated representatively, and anillustration of a fixed shaft construction in a head assembly is omittedbecause the latter construction is substantially the same as the formerconstruction.

As shown in FIG. 39, a spindle motor 26 located at the inner portion ofthe magnetic disk 24 has a first fixed shaft 26-1 constituting the mainpart of a fixed shaft 25 of spindle, that is fixed in a predeterminedposition of the base 22 within said housing 21 so as to support themagnetic disk 24 rotatably. Further, the above spindle motor 26 has apair of first bearing means 26-2 that are fixed around the fixed shaft26-1 at the upper and lower sides thereof, respectively, in order tosupport the disk fixing shaft 26-1. Furthermore, the above spindle motor26 has a spindle hub 11 that has the outer portion engaged with thecentral hole of the magnetic disk 24 and has the inner portion rotatablymounted on the fixed shaft 26-1 via the first bearing means 26-2. Also,the above spindle motor 26 has at least one rotor magnet 26-3 that isfixed to the spindle hub 11 and at least one stator coil 26-4 that isfixed to the base 22, facing the rotor magnet 26-3.

Further, a head assembly has a similar construction in respect to thedriving mechanism. More specifically, the head actuator includes a fixedsubsidiary shaft that is also fixed in a predetermined position withinthe housing 21 and includes a pair of second bearing means that arefixed around the fixed subsidiary shaft at the upper and lower sidesthereof, respectively, in order to support the fixed subsidiary shaft,as well as the magnetic head, arm and actuator as described before.

Further in FIG. 39, 15-1, 15-2 denote a first pin and a second pin,respectively, that constitute the spindle 25 together with the fixedmain shaft 26-1. The above first pin 15-1 is mainly composed of a shaftportion which has a diameter of a size that allows the first pin 15-1 tobe engaged with a central hole of the fixed main shaft 26-1 and whichhas a length shorter than the fixed shaft 26-1 and which is made ofmetal with high mechanical strength. Further, on one end of the abovefirst pin 15-1, a flange portion with a form that allows the above firstpin 15-1 to be fitted into a hole with a stepped part previously formedin the base 22 and to be finally fixed thereto by forcing plasticdeformation of the flange portion, is provided. On the other hand, thesecond pin 15-2 which forms a pair with the first pin 15-1 is mainlycomposed of a shaft portion which has a diameter of a size that allowsthe second pin 15-1 to be engaged with a central hole of the fixed shaft26-1, similar to the first pin 15-1. Further, on one end of the abovesecond pin 15-2, another flange portion, which has a diameter thatallows the second pin 15-2 to be fitted into the larger diameter portionof another hole with a stepped part previously formed in cover 23 facingthe base 22, is provided.

In the first preferred embodiment of a fixed shaft construction of adisk drive, as in FIG. 39, the flange portion of the first pin 15-1 isinserted into the hole with a stepped part of the base 22 and thenplastic deformation of the flange portion of the first pin 15-1 isperformed in such a manner that the above flange portion is enlargedtoward the outer peripheral portion thereof by means of caulking, sothat the first pin 15-1 is mounted vertically to the inside surface ofthe base 22. Further, the second pin 15-2 is inserted from the outersurface of the cover 23 into the other hole with a stepped part of thecover 23 and then is fastened to the other hole by utilizing adhesive.

To be more specific, the disk 24 and the rotor magnet 26-3 are attachedto the outer portion of the spindle hub 11, while the fixed shaft 26-1having a hollow form is fitted into the central hole of the spindle hub11, via the ball bearing means 26-2, e.g., a pair of ball bearings.Further, in the condition that the rotor magnet 26-3 of the spindle hub11 and the stator coil 26-4 are facing each other, the fixed main shaft26-1 and first pin 15-1 are fastened together by adhesive. On the otherhand, the second pin 15-1 that has already been adhered to the hole ofthe base 22, is inserted into the upper half of the fixed shaft 26-1 andis fastened to the fixed main shaft 26-1 also by adhesive. Consequently,the spindle hub 11 having the disk 24 can be successfully containedwithin a space that is constituted by the base 22 and cover 23. In thisconstruction, when a given current is supplied to the stator coil 26-4,the spindle hub 11 can rotate at a sufficiently high rate. In this case,by virtue of plastic deformation of the flange portion, the structure iswhich the fixed main shaft 26-1 rotatably supports the spindle hub 11where the disk 24 and the rotor magnet 26-3 are attached, can berealized relatively easily and with smaller dimensions and with higheraccuracy than the prior art.

FIG. 40 is a view showing a second preferred embodiment of a fixed shaftconstruction of a disk drive according to the present invention. Also inFIG. 40, similar to FIG. 39, the enlarged schematic sectional view of afixed shaft construction in a spindle motor 26 is illustratedrepresentatively.

The fixed shaft construction of the above second preferred embodiment issimilar to that of the first preferred embodiment described before.However, the construction of the second embodiment is different fromthat of the first embodiment in that another type of pin 15-3 having aform such that the pin 15-3 can be fastened to the base 22 and cover 23by welding is utilized instead of two pins 15-1, 15-2 described before.

More concretely, in a first step, the pin 15-3 is forced to pass throughthe hole with a stepped part of the base 22. In the next step, the innerend surface of the flange portion in the pin 15-3 and the bottom surfaceof the above hole with a stepped part are welded together by welding,laser spot welding or the like, so that the pin 15-3 is mountedvertically to the inside surface of the base 22. Further, the fixedshaft 26-1 that is fitted into the central hole of the spindle hub 11via the ball bearing means 26-2, is engaged with the pin 15-3 and isfastened thereto by utilizing adhesive. Further, the upper portion ofthe pin 15-3 that goes through the fixed main shaft 26-1 and protrudesthereabove, is fitted into the other hole with a stepped part of thecover 23 and is finally fastened thereto by adhesion, etc. By virtue ofwelding, laser spot welding or the like, the structure such that thefixed main shaft 26-1 rotatably supports the spindle hub 11 can berealized relatively easily and with smaller dimensions and with higheraccuracy than the prior art, similar to the first preferred embodimentshown in FIG. 39.

In the above-mentioned first and second embodiments, to fasten the fixedshaft 26-1 to the base 22 rigidly within the housing 21 having as smalla size as an IC memory card, the plastic deformation of the pin by meansof riveting and the joining of the pin with the base 22 by welding areperformed, respectively. Alternatively, it is possible for the pin to befixed to the base 22 by adhesion. In each case, preferably, the fixedshaft 26-1 is a hollow shaft and is mounted to the first bearing means26-2 by adhesion. Consequently, an assembly having a hollow form isprovided. Further, the above assembly is inserted to the pin, etc.,previously fixed to the base 22 and serving as a main central shaft.

FIG. 41 is a view showing a third preferred embodiment of a fixed shaftconstruction of a disk drive according to the present invention. Also inFIG. 41, similar to FIGS. 39 and 40, the enlarged schematic sectionalview of a fixed shaft construction in a spindle motor 26 is illustratedrepresentatively.

The fixed shaft construction of the above third preferred embodiment issimilar to that of the second preferred embodiment described before.However, the construction of the third embodiment is different from thatof the second embodiment in that integrated type ball bearings 26-6 areutilized, in which the inner race (ring) thereof and the spindle 25 arecombined into an integrated form and a given pre-load is generated bycoupling the integrated spindle with the outer race (ring) via twocolumns of balls.

As illustrated in FIG. 41, the disk 24 and the rotor magnet 26-3 areattached to the outer portion of the spindle hub 11. Further, the outerring of the integrated type ball bearings 26-6 is inserted into thecentral hole of the spindle hub 11 by pressing. Further, one end of theintegrated spindle of the above integrated type ball bearings 26-6 isforced to pass through the hole with a stepped part of the base 22, andis welded to the inner wall surface of the above hole, so that one endof the integrated spindle thereof is mounted vertically to the insidesurface of the base 22. On the other hand, the other end of the aboveintegrated spindle is fitted into the other hole with a stepped part ofthe cover 23 and is finally fastened thereto by adhesion, etc. In thiscase, since the ball bearings integrated with the spindle are used asthe ball bearing means, the process of performing a fixed shaftconstruction becomes easier than that of the first and secondembodiments as in FIGS. 39 and 40, respectively.

Furthermore, it should be noted that the second fixed shaft can befastened to the base 22 and then the second fixed shaft (thesecomponents will be illustrated in the drawings hereinafter) can bemounted to a pair of second bearing means in a manner similar to thefixed main shaft 26-1 and a pair of first bearing means 26-2.

FIG. 42 is a view for explaining the relationship of the diameter ofeach fixed shaft and the average span between each pair of bearing meansas in FIG. 39. In FIG. 42, the structure inside the housing isillustrated more briefly. Further, typical dimensions in the variousportions inside and outside the housing are noted for reference.

In this case, a thinner flange portion 25-1 is formed in the vicinity ofone end surface of spindle 25 and a straight hole is formed through thebase 22, instead of a hole with a stepped part, somewhat different fromthe first preferred embodiment in FIG. 39. Also, in this construction,the spindle 25 can be mounted vertically to the inside surface of thebase 22. In this case, preferably, the flange portion of the spindle 25(or pins 15-1, 15-3) has a diameter approximately equal to or largerthan average span S between a pair of first bearing means 26-2.

In a disk drive according to the present invention, the thicknessdimension of the housing is limited to a value smaller than 5 mm (inFIG. 42, 4.9 mm), to realize compatibility with an IC memory card. Inthis condition, since the span between a pair of bearing means is forcedto be shorter, it may be difficult to maintain precision of the positionof the bearing means in respect to the direction where they fall. Todeal with this difficulty, as in FIG. 42, the upper surface of theflange portion 25-1 is defined as the base dimension of the outerdiameter of the flange portion 25-1 and is arranged to make contact withthe lower end surface of the outer ring portions of the first bearingmeans 26-2. To realize this structure more surely, it is desirable forthe outer diameter of the flange portion 25-1 to be as large aspossible. In this case, typically, the dimension of the diameter of theflange portion 25-1 is set at a value approximately equal to or largerthan the average span S between a pair of first bearing means 26-2. Inthis construction, the ball bearing means 26-2 is practically supportedby the flange portion 25-1, as well as the body portion of the fixedshaft 25 per se. Therefore, the apparent precision of the position ofthe first bearing means 26-2 can be improved to a sufficient degree byvirtue of the increase in the base dimension of the spindle 25.

Further, it should be noted that the flange portion of a fixedsubsidiary shaft or the like also has a diameter approximately equal toor larger than the average span between a pair of second bearing means.In this construction, similar to the fixed main shaft constructiondescribed above, the apparent positioning accuracy of the second bearingmeans in respect to the direction where they fall can be improved to asufficient degree by virtue of the increase in the base dimension of thefixed subsidiary shaft or the like.

FIG. 43 is a view for explaining pre-load means on the outer ringportions of bearing means as illustrated in FIG. 39. Also, the examplein FIG. 43 in which a thinner flange portion is formed in the vicinityof one end surface of the spindle 25 and a straight hole is formedthrough the base 22, is illustrated representatively. In this case, thefirst and second bearing means can have substantially the samestructures, and therefore only the first bearing means will berepresentatively described in detail in FIG. 43.

In a disk drive according to the present invention, as already describedin FIG. 42, owing to limitation of the thickness dimension of thehousing, the span between a pair of first bearing means 26-2 is forcedto be shorter. To be more specific, the first bearing means 26-2 havethe respectively corresponding pair of outer ring portions and therespectively corresponding pair of inner ring portions. Further, pluralpairs of balls 26a are provided between the outer and inner ringportions, and the inner ring portions are attached to the fixed shaft26-1. In this construction, the upper group and lower group of theplural pairs of balls 26a as proximately overlap each other in twocolumns, with a relationship of position such that the above two groupsalmost contact each other. Accordingly, the structure of the abovebearing means 26-2 may be disadvantageous in that sufficient moment ofinertia of the spindle motor 26 is not always ensured.

To overcome this disadvantage, as in FIG. 43, pre-load means 26b, suchas a thinly-made spring means, that put a constant pressure on the outerring portions in respect to the axial direction thereof, are providedbetween a pair of outer ring portions of the first bearing means 26-2.In the drawing, the upper and lower extrapolated lines are formed byconnecting contact points where the outer and inner ring portionscontact the balls 26a, respectively. Further, when such upper and lowerextrapolated lines intersect the central line of the fixed shaft 26-1,the distance D between the intersections of the upper and lowerextrapolate lines and the central line is longer than the average span Sbetween a pair of first bearing means 26-2, by means of the pressure onthe outer ring portions. For example, in FIG. 43, the distance D becomesapproximately twice as large as the average span S. Consequently, themoment of inertia of the spindle motor 26 can be substantiallyequivalent to the moment of inertia generated by the a pair of bearingmeans having the average span therebetween approximately twice as largeas the actual average span S.

FIGS. 44, 45 and 46 are views showing a fourth preferred embodiment of afixing shaft construction of a disk drive according to the presentinvention. To be more specific, FIG. 44 is a sectional front viewshowing a structure inside the housing of the fourth preferredembodiment; FIG. 45 is a perspective view showing a structure inside thehousing with the cover removed; and FIG. 46 is an enlarged sectionalview showing the main part of FIG. 45. In FIG. 46, the description of aconnector as shown in FIG. 45 is omitted to simplify the explanation ofthe fourth preferred embodiment of a fixed shaft construction. Further,in this case, to emphasize the characteristics of the above fourthembodiment, a fixed shaft of spindle is indicated by the referencenumeral 18, not 26-1 as in FIGS. 39 to 43.

In these figures, a head assembly has two magnetic heads 27 that executereproducing/recording operations corresponding to read/write operationsof the information on the upper and lower surfaces of a magnetic disk24, two arms 28 that movably support the above two magnetic heads 27,and an actuator 29 that forces the arms 28 to rotate in either directionand the magnetic heads 27 to move to predetermined tracks on themagnetic disk 24. Further, the cover 23 desirably functions not only asshielding means that electromagnetically shields various componentsinside the housing 21 from the external magnetic field, but also as dustprotective means that prevents dust particles from adhering to amagnetic disk 24, magnetic heads 27 or the like. To realize the abovetwo functions of the cover 23, as illustrated in FIG. 44, the cover 23is constructed to be coupled to the base 22 by utilizing appropriatefastening means, e.g., screws and pins, or a packing, etc., insertedbetween the cover 23 and the peripheral portion 22' of the base 22, sothat the cover 23 is glued to the peripheral portion 22' without anyclearance.

Further, the fixed main shaft 18 located between the base 22 and cover23 at the side of the magnetic disk 24 is fastened to the above base 22and cover 23 in the form of a fixed beam. A pair of first bearing means26-2 are fitted around the above fixed shaft 18, and via the above firstbearing means 26-2, a spindle hub 11 is rotatably supported by the abovemain shaft 18. The magnetic disk 24 is coupled with the outer peripheralportion of the spindle hub 11 in a unified form and the above spindlehub 11 rotates with the magnetic disk 24.

On the other hand, the second fixed shaft 45 located between the base 22and cover 23 at the side of the actuator 29 is also fastened to theabove base 22 and cover 23 in the form of a fixed beam. A pair of secondbearing means 46 are fitted around the above fixed shaft 45, and via theabove second bearing means 46, two arms 28 are rotatably supported bythe above fixed shaft 45. The two arms 28 consist of an arm supportingpart 17 having a supporting hole 17a into which the above second bearingmeans 46 is fitted, and two head supporting elements 28-1 that are heldby a pair of projections 17b, 17c, both of which are projected outwardfrom the arm supporting part 17. In this case, each of the aboveprojections 17b, 17c are in the form of a thin sheet and extend in thehorizontal direction. Further, the two magnetic heads 27 that face theupper and lower surfaces 24a, 24b of the magnetic disk 24, are supportedon the respective tip portions of the two head supporting elements 28-1.

Further, a mounting portion 17d is projected a direction opposite to thearm supporting part 17 of the arms 28. A movable coil portion 29b isfixed on the mounting portion 17d, and a magnet portion 29a contacts theinner wall surface of the cover 23. Furthermore, a yoke portion 29c isfixed on the inner wall surface of the base 22 facing the lower surfaceof the mounting portion 17d. In this construction, the arm 27 can beallowed to rotate in both directions by the driving force caused by theactuator 29 having the movable coil portion 29b, the magnet portion 29aand the yoke portion 29c. Consequently, the tracking of a disk drive forreproducing/recording operations can be performed by moving the twomagnetic heads 27 relative to the magnetic disk 24.

Next, the mounting structure of the fixed shaft 18 of the two kinds offixed shafts will be representatively described in more detail. As shownin FIG. 46, a threaded female part 18b, into which a fixing screw 43 isscrewed, is formed in the bottom end surface 18a of the fixed shaft 18.Further, a stepped portion 18c is formed on the upper part of the fixedmain shaft 18. Above this stepped portion 18c, a smaller diameterportion 18c protrudes upward from the fixed main shaft 18 in the axialdirection. In this case, the smaller diameter portion 18d has a diameterd that is smaller than the outside diameter D of the fixed shaft 18.

Further, the length T₁ measured from the bottom end surface 18a of thefixed shaft 18 through the stepped portion 18c thereof is slightlylarger than the distance L₂ between the upper surface 22b of the base 22and the lower surface of the cover 23 (in the fourth preferredembodiment as illustrated in FIGS. 44 to 46, about 0.02-0.04 mm).Further, an insertion hole 22c, into which the fixing screw 43 isinserted, is formed in the base 22. Also, a through hole 23b is formedin a top portion 23a of the cover 23 facing the insertion hole 22c. Inthis case, the inside diameter D₁ of the through hole 23b is made largerthan the outside diameter d of the fixed shaft 18 (D>D₁ >d).

When the fixed shaft 18 is fastened to the base 22 and cover 23, in afirst step, the fixing screw 43 is inserted from the insertion hole 22cinto the threaded female part 18b and is screwed down, so that the fixedshaft 18 is standing firmly on the base 22. In the next step, the cover23d is mounted on the base 22 so that the smaller diameter portion 18dof the fixed shaft 18 can be inserted into the through hole 23b of thecover 23.

As described above, since the outside diameter D of the fixed main shaft18 is larger than the inside diameter D₁ of the through hole 23b, thestepped portion 18c of the fixed shaft 18 can contact the lower surface18c of the cover 23. Moreover, since the length T₁ from the bottom endsurface 18a through the stepped portion 18c is slightly larger than thedistance L₂ between the upper surface 22b of the base 22 and the lowersurface of the cover 23, the fixed shaft 18 forces the peripheralportion of the through hole 23b of the cover 23 to be lifted upward.Therefore, the top portion 23a of the cover 23 is pressed upward and isslightly deformed into a bent form as illustrated in FIG. 46.Consequently, the cover 23 is constructed to hold the fixed shaft 18 bypressing downward on the stepped portion 18c of the above shaft 18, in aform of a diaphragm.

In this condition, adhesive 44 that serves as the fastening means andsealing means is injected into the space between the through hole 23band the smaller diameter portion 18d from the upper side of the cover 23and finally the cover 23 is adhered to the fixed main shaft 18 by heatcuring or ultravioleted irradiation of the adhesive 44. Preferably,epoxy elastic adhesive, etc., that has high viscosity and low hardnessafter heat curing, is utilized as the adhesive 44 shown in FIGS. 44 and46. In this case, if the viscosity of the adhesive 44 is sufficientlyhigh, the adhesive 44 can be prevented from penetrating past the cover23 even when the adhesive 44 is poured into the through hole 23b.Further, if the hardness after heat curing of the adhesive 44 issufficiently low, the smaller diameter portion 18d of the fixed shaft 18can be elastically fastened to the through hole 23b via the adhesive 44.Furthermore, by virtue of the injection of the adhesive 44, the throughhole 23b become closed and therefore dust floating in the air can beprevented from going through the cover 23. Accordingly, the adherence ofdust to the magnetic disk 24 and the magnetic heads 27 and theirsurfaces resulting in damage thereto, can be prevented.

In other words, in the fourth preferred embodiment as illustrated inFIGS. 44 to 46, the fixed shaft 18 is constructed to be coupled with thecover 23 rigidly in respect to the thickness direction of the housing 21by firmly pressing downward against the stepped portion 18c of the abovefixed shaft 18, and coupled with the cover 23 flexibly in respect to theplane directions thereof by utilizing the elastic adhesive. By virtue ofthis construction, thermal stress, etc., which may be caused by thestructure in which the fixed shaft 18 is fastened rigidly to both thebase 22 and cover 23 in all directions, can be relieved.

More concretely, the cover 23 is mounted on the base 22 and further isfastened thereto by adhesive so that the upper part of the fixed mainshaft 18 can be securely fixed to the cover 22. In this case, since thesmaller diameter portion 18d is intended to be fitted into the throughhole 23b with appropriate looseness, the fixed main shaft 18 can beprevented from tilting due to tightening thereof with a screw as in theprior art. Accordingly, it becomes possible for even inexperiencedworkers to perform the process of mounting the cover 23 on the base 22relatively easily. Further, the condition of the fixed shaft 18 verticalto the base 22 can be maintained even after the cover 23 is fixed to thebase 22. Therefore, tilting of the spindle hub 11 and the disk 24mounted on the fixed main shaft 18, can be avoided, and the spindle hub11 and the disk 24 can be stably supported by the fixed shaft 18 in apredetermined position. Consequently, since the relative position of thetwo magnetic heads 27 in respect to the magnetic disk 24 can becontrolled with high precision, it becomes possible for the trackingcontrol in reproducing/recording operations to be performed moreaccurately than in the prior art and the demand for higher magneticrecording density can be satisfied.

Further, the above-mentioned mounting structure of the fixed shaft 18 ofa spindle can be applied to the fixed shaft 45 of the actuator. Namely,the fixed shaft 45 of the actuator has substantially the same mountingstructure as that of the fixed shaft 18 of the spindle. Here, thedetailed description of such fixed shaft 45 is omitted. Briefly, thefixed subsidiary shaft 45 stands on the base 22 in a vertical directionwithout tilting, together with the fixed shaft 18. Therefore, the arm 28can be prevented from tilting and position errors of the magnetic head27 in respect to the upper and lower surfaces of the disc 24 can beavoided.

FIG. 47 is a view showing one example of a change in a fixing structureof the shaft and cover in the embodiment as illustrated in FIG. 46. Inthis case, the main part of the fixing structure of the shaft and coveris illustrated in enlargement.

In FIG. 47, instead of the above-mentioned adhesive 44, an elasticsealing member, e.g, an O ring 44-1 made of rubber is placed between thesmaller diameter portion 18d of the fixed shaft 18 and the through hole23b of the cover 23. In this case, since the O ring 44-1 has elasticity,it is deformed into an elliptical form by exerting pressure on the Oring 44-1 from the inner and outer portion thereof. In this condition,the O ring 44-1 can be glued to the outer circumference of the smallerdiameter portion 18d and the inner circumference of the through hole 23bwithout any clearance, and the sealing of the space between the smallerdiameter portion 18d and the through hole 23b can be performed securely.By virtue of the elasticity of O ring 44-1, dust floating in the air canbe prevented from going through the cover 23. Accordingly, dust adheringto the magnetic disk 24 and the magnetic heads 27 and their surfaces andcausing injury can be avoided, similar to the embodiment as illustratedin FIG. 46.

There can be proposed a method based on welding as another embodiment ofcoupling the fixed shaft 18 without inclining it to the cover 23 asshown in FIG. 46. As shown, for instance, in FIG. 43, the fixed shaft18(26-1) does not have a step at the upper end surface thereof, and thethrough hole is not formed in the cover 23, either. The upper end of thefixed shaft 18 comes in contact with the cover 23 under the conditionwhere the base 22 and the cover 23 are fastened together. When they donot come in contact with each other due to tolerance in the size, thecover 23 is lightly depressed. Under this condition, the spot welding iseffected from the upper surface of the cover 23. The cover 23 is weldedat the last step of assembling where electronic parts have all beencontained in the inside. Therefore, the laser welding is preferred tothe electric welding. Thus, the fixed shaft 18 is reliably fastened tothe cover 23 without exerting any force in the direction to tilt thefixed shaft 18.

FIGS. 48 and 49 are views showing a fifth preferred embodiment of afixed shaft construction of a disk drive according to the presentinvention. To be more specific, (A) of FIG. 48 is a front view showingthe structure inside the housing and (B) of FIG. 48 is a sectional viewtaken along a line B--B of (A). Here, only the main part of the fixedshaft construction relating to the characteristics of the fifthpreferred embodiment is illustrated. Further, in FIG. 49, either one oftwo common portions indicated by E of FIG. 48(B) is illustratedrepresentatively.

As shown in FIGS. 48 and 49, the fixed subsidiary shaft 45 hassubstantially the same mounting structure as that of the fixed mainshaft 18, including the screw 43 and the bearing means 19, 46. Inparticular, with regard to the bearing means having a relativelycomplicated structure, it should be noted that the first bearing means19 of the spindle motor 18 has substantially the same construction asthe second bearing means 46 of the head assembly. Accordingly, thefundamental parts of such bearing means can be designed and fabricatedwith common specifications. Therefore, the kind of mechanical componentswithin the housing can be reduced an the total cost for fabricating adisk drive becomes lower.

Hereinafter, various embodiments of a whole spindle motor constructionof a disk drive according to the present invention will be describedwith reference to FIG. 50 to FIG. 57.

FIG. 50 is a view showing a first preferred embodiment of a wholespindle motor construction of a disk drive according to the presentinvention. In FIG. 50, the main part of the spindle motor constructionrelating to the characteristics of the first preferred embodiment isillustrated.

As shown in FIG. 50, a fixed shaft 25 is fastened to the base 22 andcover 23 in order to hold the spindle motor 26 per se in a predeterminedposition within the housing 21 so that one magnetic disk 24 can rotatetherein. A pair of first bearing means 26-2 (from now on, "first" willbe omitted) are fixed around the spindle 25 in order to support thefixed shaft 25. Further, a spindle hub 11 has an outer portion engagedwith the central hole of the magnetic disk 24 and has an inner portionrotatably mounted on said fixed shaft 25 via the bearing means 26-2. Inthis case, a rotor magnet 26-3 is composed of a permanent magnet havingthe form of a flat plate that is magnetized in the axial direction ofthe fixed shaft 25, and is fitted into a recessed portion of the bottomsurface of the spindle hub 11 and is finally adhered thereto. In theabove first embodiment, the spindle hub 11 is made of a soft magneticmaterial that can be utilized as a yoke. Alternatively, if a nonmagneticmaterial is used for the spindle hub 11, the rotor magnet 26-3 isadhered to this spindle hub 11 via another yoke. In this case,preferably, an outer ring rotating motor in which the outer ring portionof the bearing means 26-2 rotates is utilized as the spindle motor 26.

Further, a stator coil 26-4 is fixed on the upper wall surface of thebase 22 inside the housing 21, so that the stator coil 26-4 faces therotor magnet 26-3, close to the rotor magnet 26-3 with a certain axialgap. To be more specific, the rotor magnet 26-3 is located between theposition of the inside diameter of the magnetic disk 24 and the positionof an outer peripheral portion of the bearing means in respect to theradial direction of the rotor magnet 26-3. The base 22 that constitutesa part of the housing 21 is made of a soft magnetic material and alsoserves as a stator yoke. Here, the stator coil 26-4 is located in a sucha manner that it protrudes toward the space near the magnetic disk 24inside the housing 21.

In this construction of the spindle motor, a face-to-face type motor,i.e., a flat type motor, utilizing the magnetic flux in the axialdirection of the spindle 25 between the rotor magnet 26-3 and statorcoil 26-4, can be formed, and the spindle hub 11 and the magnetic disk24 rotate in an integrated form with the rotor magnet 26-3 in accordancewith the rotation thereof. In this case, the thickness of the spindlemotor per se can become remarkably small. By using the face-to-face type(axial gap) motor, the almost inside of the motor can be covered withthe bearing as seen from FIG. 42, and also the outer diameter of themotor can be smaller than the inner diameter, and thereby the drivehaving a thickness of lower than 5 mm can be realized.

Further, since at least the base 22 is made of a soft magnetic materialand acts as a yoke simultaneously, a disk drive, in which excellentcharacteristics can be ensured with smaller size and lower weight than aprior art disk drive, can be provided. In particular, the abovestructure can be effectively applied to a disk drive utilizing a smallnumber of magnetic disks.

FIG. 51 is a view showing a second preferred embodiment of a wholespindle motor construction of a disk drive according to the presentinvention. Also in FIG. 51, the main part of the spindle motorconstruction is illustrated.

The construction of the above second preferred embodiment is similar tothat of the first preferred embodiment as shown in FIG. 50. However, inthe second embodiment, different from the first embodiment, each of thespindle hub 11, base 22 and cover 23 is made of a non-magnetic material.In this case, the rotor magnet 26-3 is arranged to have a largerthickness than that of FIG. 50, and the stator yoke at the cover side isutilized, instead of the rotor yoke, as a magnetic path. By arrangingthe rotor magnet 26-3 in this way, the effective magnetic flux can beincreased and excellent motor characteristics can be ensured, similar tothe first preferred embodiment as illustrated in FIG. 50.

Further, on the surface of the lower side wall, a stator yoke 26-10 islocated in position opposite to the stator coil 26-4 across the spindlehub 11. Furthermore, since the base 22 is made of non-magnetic materialas described above, a bushing 22-10 serving as another stator yoke isfixed to the base 22 by screws 22-11 to obtain the effective magneticflux. The method of fixing a stator yoke to the base 22 can be alsoapplied to any other embodiment utilizing the stator yoke.

In the above second preferred embodiment, owing to the non-magneticspindle hub 11, base 22 and cover 23, the process of fixing the statoryoke to the base 22 and cover 23 becomes necessary. However, if theabove spindle hub 11, base 22 and cover 23 are composed of non-magneticmetal, e.g., aluminum having a smaller specific gravity than theconventional soft magnetic material, the above second embodiment has anadvantage that the moment of inertia of each of the rotating componentssuch as the spindle hub 11 and rotor magnet 26-3 can be decreased.Further, since the above rotating components are not used for a yoke,there is another advantage in that the thickness of the spindle hub 11,etc., can become smaller than that of the first embodiment asillustrated in FIG. 50.

FIG. 52 is a view showing a third preferred embodiment of a wholespindle motor construction of a disk drive according to the presentinvention. Also in FIG. 52, the main part of the spindle motorconstruction is illustrated.

The construction of the above third preferred embodiment is similar tothat of the first preferred embodiment as shown in FIG. 50. However, inthe third embodiment, different from the first embodiment, two rotormagnets 11-1, 11-2, that are magnetized in the same direction as theaxial direction of the fixed shaft 25, are fixed to the lower and uppersides of the spindle hub 11, respectively. Further, the lower statorcoil 26-4a is fixed on the upper wall surface of the base 22 inside thehousing 21, so that the lower stator coil 26-4a faces the lower rotormagnet 11-1, close to the lower rotor magnet 11-1 with a certain axialgap. On the other hand, the upper stator coil 26-4b is fixed on thelower wall surface of the cover 23, so that the upper stator coil 26-4bfaces the upper rotor magnet 11-2, close to the upper rotor magnet 11-2with a certain axial gap.

As described above, in the above third preferred embodiment, two statorcoils 26-4a, 26-4b, and the base 22 and cover 23, both of which serve asa stator yoke, are located in symmetrical positions at the lower andupper sides of the spindle hub 11 in respect to the center of thethickness direction of spindle hub 11, respectively. Therefore, twosources of magnetic attraction that are generated between two rotormagnets 11-1, 11-2 and the respectively corresponding base 22 and cover23, balance each other out. Consequently, the thrust load of bearingmeans 26-2 can be reduced and a disk drive having a longer life can berealized.

Further, in the above third preferred embodiment, since two equivalentface-to-face motors exist, a relatively large torque can be attained.Furthermore, the stator coils are arranged to be separated into thelower coil 26-4a and the upper coil 26-4b. Therefore, a sufficientlylarge torque can be generated in a wake-up operation of the motor bycombining the two stator coils, while either one of the stator coils canbe separated from the other one and the back electromotive force can bereduced during constant speed rotation of the motor, which leads to therotation of the disk at a higher rate.

FIG. 53 is a view showing a fourth preferred embodiment of a wholespindle motor construction of a disk drive according to the presentinvention. Also in FIG. 53, the main part of the spindle motorconstruction is illustrated.

The construction of the above fourth preferred embodiment is similar tothat of the second preferred embodiment as shown in FIG. 51. However, inthe fourth embodiment, different from the second embodiment, a rotormagnet 26-7 is made of an annular permanent magnet and the innerperipheral portion thereof is rotatably supported by the fixed shaft 25,not by a spindle hub, via the bearing means 26-2. Further, the outerperipheral portion of the rotor magnet 26-7 is arranged to be fittedinto the central hole of the disk 24. In other words, the rotor magnet26-7 of the fourth embodiment as illustrated in FIG. 53 also serves asthe spindle hub. Further, the cover 23 is made of a soft magneticmaterial and has a form such that the above cover 23 is as close to therotor magnet 26-7 as possible, so that the above cover 23 serves as astator yoke instead of a rotor yoke. In this construction, theelimination of relatively large mechanical components such as thespindle hub can be realized, and therefore a disk drive with smallerdimensions and lower weight can be realized.

FIG. 54 is a view showing a fifth preferred embodiment of a wholespindle motor construction of a disk drive according to the presentinvention. Also in FIG. 54, the main part of the spindle motorconstruction is illustrated.

The construction of the above fifth preferred embodiment is similar tothat of the fourth preferred embodiment as shown in FIG. 53. However, inthe fifth embodiment, different from the fourth embodiment, a spindlehub 11 has an approximately annular form and is divided into pluralsections in the axial direction of the fixed shaft 25. The rotor magnet26-8 is adhered to the above spindle hub 11 as an intermediate member.Further, the above rotor magnet 26-8 is magnetized in the same directionas the axial direction of the spindle 25. Furthermore, the above rotormagnet 26-7 is constructed to have a thickness such that the upper andlower magnetized surfaces thereof face the cover 23 and the stator coil26-4, as close to the cover 23 and the stator coil 26-4 as possible,respectively.

The above fifth preferred embodiment of the whole spindle motorconstruction has the same advantage as other embodiments of the motorconstruction in that excellent characteristics can be ensured with asmaller size and lower weight than the prior art by virtue of the novelarrangement of the rotor magnet.

Further, it is made easy to support the disk, which is difficult in thefourth embodiment, by utilizing easy machinable materials, and therebyhigh accuracy in height of the disk can be attained.

FIG. 55 is a view showing a sixth preferred embodiment of a wholespindle motor construction of a disk drive according to the presentinvention. In FIG. 55, the main part of the spindle motor construction,especially the main part of the structure for mounting a magnetic diskon a spindle hub illustrated. In this case, a fixed shaft 25, a pair ofbearing means 26-2, a rotor magnet 26-3 and a stator coil 26-4 havesubstantially the same interrelationship as the first preferredembodiment illustrated in FIG. 50 as already described.

In a conventional mounting structure of a magnetic disk, at least onemagnetic disk 24 is fixed to a spindle hub 11 by locking clamp meansplaced on the magnetic disk 24 and attached to the spindle hub 11 bymeans of screws. On the other hand, in the sixth preferred embodiment asin FIG. 55, the magnetic disk 24 is engaged with a spindle hub 11 viaadhesive 47, e.g., light-hardening type adhesive, and is finally fixedto the above spindle hub 11 by curing the adhesive 47 by irradiationwith UV (ultraviolet) light, instead of utilizing clamp means andscrews.

In this construction, the disk fixing structure can become simpler thanthe prior art, and some constituent components such as clamp means andscrews in the prior art become unnecessary. Therefore, the number of theconstituent components can be decreased and space utilized within thehousing can be reduced. Consequently, the thickness dimension of thehousing 21 can become smaller than the prior art and the whole diskdrive can have as compact a size as an IC memory card of Type IIaccording to the PCMCIA.

FIG. 56 is a view showing one example of a change in a disk fixingstructure in the sixth preferred embodiment as illustrated in FIG. 55.Also in FIG. 55, only the main part of the spindle motor construction isillustrated.

The construction of the FIG. 56 is similar to that of the sixthpreferred embodiment as shown in FIG. 55. However, in this construction,as in the construction of the sixth embodiment, a recessed part 47-1having a form that allows adhesive 47 to be stored previously, e.g., atriangular section, is provided on the respective adhering surfaces of aspindle hub 11 and a magnetic disk 24, which contact each other. In thiscase, when the magnetic disk 24 is adhered to the spindle hub 11 by theadhesive 47, such as a light-hardening type adhesive, the above recessedpart 47-1 is arranged to be full of a sufficient amount of the adhesive47. Therefore, it becomes possible for the adhesive strength of theabove two adhering surfaces to be increased more than in the caseillustrated in FIG. 55.

In each of the disk fixing structures as illustrated in FIGS. 55 and 56,it is necessary that the adhesive 47 be uniformly spread over the wholearea of the respective adhering surfaces of the spindle hub 11 andmagnetic disk 24, and that it is uniformly fixed over the whole areathereof by equally curing the adhesive 47 by irradiation with UV(ultraviolet) light. In this case, a light-hardening type adhesive ispreferably utilized as the adhesive 47. As another example, anaerobicadhesive may be utilized in the region which is not exposed to the air,while another adhesive simultaneously having an ananaerobic property anda light-hardening property capable of hardening by irradiation with UVlight may be utilized in the region which is exposed to the air.

Further, the form of the recessed part 47-1 is not limited to that of atriangular section described before with reference to FIG. 56. Forexample, the form of such recessed part 47-1 may be that of asemicircular section, a rectangular form and other various forms.Furthermore, a plurality of recessed parts, each of which has one of theabove-mentioned various forms and which are combined into continuousgrooved forms as a whole, may be provided alternatively. In this case,it is preferable that the above recessed parts be located so that theycan be distributed with respectively equal spaces in respect to thecircumferential direction of the fired shaft 25.

As described above, in this construction, the uniform spread of theadhesive 47 on the respective adhering surfaces of the spindle hub 11and magnetic disk 24 can be ensured and also uniform fixing by curingthe adhesive 47 of the above respective adhering surfaces can beensured, and further the uniform distribution of a plurality of recessedparts can be performed. Therefore, when the spindle hub 11 to which themagnetic disk 24 is fixed rotates, a disadvantageous imbalancephenomenon in which the bearing means 26-2 vibrate due to thenonuniformity of the adhesive 47 in fastening together the aboverespective adhering surfaces, unequal distribution of recessed parts andthe like, can be reduced to a minimum level.

Further, if the above imbalance phenomenon may occur when the spindlehub 11 rotates with the magnetic disk 24, in a first step, rotatingcomponents such as the spindle hub 11 can be placed on a test mount ofan apparatus for testing the degree of imbalance in such a manner thatthe occurrence of the vibration of the spindle hub 11 is not restricted.In a second step, some positions in the adhering surfaces, in which theabove imbalance must be corrected, are determined by evaluating thedirection of imbalance (phase angle) and the amount of imbalance. In athird step, as typically illustrated in FIG. 57, a required amount ofweight correcting elements 11a made of light-hardening resin,thermohardening resin or the like are attached to the above determinedpositions on the adhering surfaces other than the recording regions onthe magnetic disk 24. In a fourth step, the above correcting weightelements 11a are cured by means of UV light, high temperature or thelike. In this case, to adjust the value of specific gravity of theweight correcting elements 11a, metal powder, etc., is preferably mixedwith the above resin. Finally, by virtue of the cured resin serving asthe correcting means, the imbalance phenomenon can be securelysuppressed.

FIG. 58 is a diagram illustrating a modified example of the frame ofFIG. 38. In FIG. 58, a portion of the U-shaped frame 33 of FIG. 38 isemphasized in a circle of a dot-dash chain line.

In the magnetic disk drive constitution of the present invention, themagnetic disk drive is considerably firmly supported by the connector42. However, a gap inevitably exists between the housing 21 of themagnetic disk drive and the frame that works as an insertion guideportion for inserting the magnetic disk drive in the external hostcomputer. Therefore, after insertion of the housing 21 into the slot ofthe host computer, if a read/write operation across a plurality of thetrucks is carried out very frequently and vigorous seek movement(movement of the head) is performed, the magnetic disk drive also movesvigorously due to the reaction caused by the motion of the magnetichead. Therefore, there may generate abnormal noise. In order to avoidgeneration of abnormal noise, therefore, it becomes necessary tominimize the looseness between the housing and the frame.

In order to substantially suppress the looseness in FIG. 58, a protrudedportion 33-1 which slightly protrudes beyond the line of the whole outershape is formed on a portion of the frame 33 (shown in a circle of adot-dash chain line on an enlarged scale). The protruded portion 33-1 isformed on only a portion of the frame 33 and can have a function likethat of a spring. In this case, the protruded portion 33-1 should bepositioned on the outer side (opposite side to the insertion) as much aspossible, so that the frame 33 is not caught at the inlet of the slotwhen the housing 21 is inserted, and the frame 33 must be as soft aspossible for the slot. In order to make the frame 33 further soft, aslit 33-2 may be formed on the inside of the protruded portion as shownin FIG. 59. As shown in FIG. 60, further, a resilient means 33-3 such asa thin metallic leaf spring may be insert-molded in the frame 33 made ofa plastic member in order to completely absorb the looseness.

The resilient means 33-3 should be inserted in the direction of theinner surface from the viewpoint of its function. In practice, however,the similar effect can be obtained even when it is inserted in theup-and-down direction because of the force of friction.

FIGS. 61 to 67 are diagrams illustrating a locking structure of the headassembly in the magnetic disk drive of the present invention. Ifdescribed in further detail, FIG. 61 is a plan view which schematicallyillustrates the locking structure of the head assembly of the presentinvention, FIG. 62 is a sectional view showing partly on an enlargedscale the sealing structure for the interior of the housing and theregion where the rod is disposed, FIG. 63 is a perspective viewexplaining the inserting/removing operations of the magnetic disk drivefor the personal computer, FIG. 64 is a plan view which explains indetail a second locking structure of the head assembly of the presentinvention, FIG. 65 is a front view showing partly in cross section thesecond locking structure of the head assembly of the present invention,FIGS. 66(A), 66(B) and 66(C) are a plan view, a front view and a sideview of constituent parts that directly engage with the locking of theactuator, and FIGS. 67(A) and 67(B) are a plan view and a front viewwhich illustrate in detail and partly in cross section the structure ofthe rod.

Even in FIGS. 61 to 64 like in the above-mentioned case, there arearranged in the housing 21 a piece of magnetic disk 24 that is mountedon the spindle 12 and a head-positioning actuator 29 that supports, viaa support spring (not shown) and an arm 28, the magnetic head 27 whichrecords and reproduces information to and from the magnetic disk 24.

Near the outer circumference of the magnetic disk 24 are arranged aload/unload member 54 which performs a loading or unloading of themagnetic head 27 relative to the magnetic disk 24, and a stopper 53which locks the actuator 29 near the outside of the arm 28 when themagnetic head 27 is unloaded. On a side portion along the magnetic disk24 and the actuator 29, there is disposed a rod 52 that works as a drivebar having a coil spring 51 attached at its one end and that moves inthe lengthwise direction thereof as indicated by arrow. Theaforementioned loading/unloading operations are carried out beinginterlocked to the inserting/removing operations at the time when thehousing 21 of the magnetic disk drive is inserted in or removed from theslot 60-1 of the external host equipment 60 (FIG. 61).

Furthermore on the rod 52 with coil spring 51 are supported, via supportshafts 57-1 and 57-2, a first lock lever 52a having a pad 56 that ismade of a rubber and that works as a packing for locking the magneticdisk being interlocked to the motion of the rod 52 in the lengthwisedirection thereof, and a second lock lever 52b which pushes the arm 28onto the stopper 53, the first lock lever and the second lock leverbeing linked to each other by two protruded pins 55. If concretelydescribed, the rod 52 is installed inside the frame 33 (see FIGS. 58 to60) mounted on the outer periphery of the housing 21, and the end of therod protrudes to the side position of the connector terminal 22-1.

On the outer side surface of the housing 21 are provided an operationhole 58 for pushing the other end of the rod 52 to actuate it, and theconnector terminal 22-1 that works for inputting and outputting data orsignals and supplying power. The thus constituted disk drive 20 can beremovably inserted in the slot 60-1 of the host computer 49 (FIG. 63) orthe like equipment that has a connector terminal 60-2 which correspondsto the connector terminal 22-1 and an operation protrusion 59 thatpushes the other end of the rod 52 to actuate it, which are formed onthe inner end surface thereof.

The interior of the housing 21 and the region where the rod 52 isdisposed are sealed by fitting an O-ring 57a to the support shaft 57-2that supports the second lock lever 52a as shown in a partly enlargedsectional view of FIG. 62. Therefore, the interior of the housing 21 isair-tightly shut off from the open air.

When the disk drive 20 is inserted in the slot 61 of the host computer49 as shown in FIG. 63, the connector terminal 60-2 on the side of theslot 60-1 is connected to the connector terminal 22-1 on the side of thedisk drive 20 as clearly shown in FIG. 61. Further, the operationprotrusion 59 of the side of the slot 60-1 pushes the other end of therod 52 of the side of the magnetic disk drive 20. Being interlocked tothis pushing operation, the magnetic disk 24 is slightly turned, and thearm 28 which supports the magnetic head 27 in an unloaded condition onthe load/unload member 54 is pushed onto the stopper 53. Then, thesecond lock lever 52b locking the actuator 29 and the first lock lever52a having pad 56 that is pressing and locking the magnetic disk 24 arerotated in the directions to liberate the locked condition. Therefore,the magnetic disk 24 is rotated, the magnetic head 27 is loaded, and thememory becomes accessible.

When the disk drive 20 is taken out from the slot 60-1, the rod 52 movestoward the operation hole 58 being urged by the coil sprint 51, and thefirst lock lever 52a having pad 56 and the second lock lever 52b areturned being interlocked thereto. By this, the magnetic disk 24 isprevented from rotating by the pad 56 mounted on the first lock lever52a. The head arm 28 supporting the magnetic head 27 is pushed onto thestopper 53 by the second lock lever 52b, whereby the magnetic head 27 isunloaded on the load/unload member 54 and, at the same time, theactuator 29 is locked.

Moreover, the magnetic disk 24 and the actuator 29 may be locked andunlocked by a mechanism which is shown, for example, in FIG. 63 in whichwhen a closure 49a of the host computer 49 is closed with the disk drive20 being inserted in the slot 60-1 of the host computer 49, a protrudedpin 49b is depressed to actuate the rod 52 on the side of the disk drive20 so that the magnetic disk 24 and the actuator 29 are locked, and whenthe closure 49a is opened, the protruded pin 49b is liberated from thedepressed condition to liberate the locked condition.

In this case, the opening portion of the slot 60-1 of the host computermay be provided with a closure that opens and closes being interlockedto the operation for inserting and removing the disk drive 20. Theabove-mentioned locking mechanism makes it possible to insert or removethe disk drive in or from such equipment as a host computer whileenabling the interior of the magnetic disk drive to be hermeticallysealed from the external atmosphere. Being interlocked to the insertingand removing operations, furthermore, the magnetic head can be loadedand unloaded and, furthermore, the disk and the actuator can be lockedand unlocked. Therefore, the disk drive is protected from sudden shocksthat may develop when the host computer is being handled or carried.Thus, there is provided an IC memory card-type disk drive featuringexcellent advantages in safety and reliability.

A second embodiment of the mechanism for locking the magnetic head 27will now be described in conjunction with FIGS. 64 to 67.

In FIGS. 64 and 65, reference numeral 51-1 denotes a leaf spring, 51-2denotes an operation lever and 51-4 denotes a pin. When the housing 21of the magnetic disk drive 20 is inserted in the host computer 49, therod 52 (FIG. 61) such as a push lever 51-3 is depressed, and theoperation lever 51-2 moves and the actuator 29 is allowed to move, too.Therefore, the magnetic head 27 assumes the loaded condition and thememory becomes accessible. When the housing 21 is pulled out from thehost computer, furthermore, the actuator 29 returns to the initialposition due to the restoring force of the leaf spring 51-1, and themagnetic head 27 assumes the unloaded condition.

The card-type magnetic disk drive 20 will encounter the severestcondition in which it is likely to be damaged when the magnetic diskdrive that is being transported is inadvertently fallen. In order tocope with the case when the magnetic disk drive is fallen that createsthe severest condition, a mechanism is employed which effects thelocking when the housing 21 is removed from the slot as describedearlier. That is, the straight rod 52 supported by a spring such as leafspring is arranged by the side of the connector so that, when thehousing 21 is removed from the slot 60-1, the rod 52 displaces towardthe outer side due to the restoring force of the leaf spring or a likespring, and that the locking is effected by the residual pressure of thespring. By taking into consideration the imaginary rotational angularacceleration at the time of falling, the pre-load is selected to producea pre-load moment that is not smaller than a torque produced by thepre-load moment of inertia of the actuator 29. Concretely speaking, thedevice is so designed that the actuator 29 does not move even when anacceleration of 1000 G (122000 rad/s² reckoned as an angularacceleration) is applied to a corner of the long side of the card withits opposite corner being fixed.

The rod 52 extends along the frame 33 from a portion of the connector 42through up to the side portion of the actuator 29. In this case, one endof the rod 52 is designed to appear in a trench close to the connector,which trench is defined as one for preventing erroneous insertionaccording to the specification of PCMCIA, and when an insertion is madeto the slot according to the specification of PCMCIA, the end of the rodis pushed. The rod 52 is provided with a partly arcuate under-cutsemi-circular hole (see L-L cross section of FIG. 67(B)) formed in aresin molded part such as the frame 33, and the rod 52 is guided throughthis semi-circular hole and a hole which is constituted by theperipheral edge of the base 22 (see K-K cross section of FIG. 67(B)).The side portion of the cover is partly cut away to form a hole throughwhich the operation lever 51-2 extends from the side of the actuator 29to come in contact with a rod 82. The operation lever 51-2 is pushed tothe side of the connector 42 by the leaf spring 51-1 located at the backof a magnetic circuit that will be described later. The rod 52 has acenter of rotation by the side of the magnetic circuit and has asickle-shaped end which pushes the actuator 29 to lock it. When the rod52 is under the liberated condition, the pre-load pressure of the leafspring 51-1 causes the magnetic head 27 to be pushed and locked on theouter side. When the housing 21 is inserted in the slot 60-1, on theother hand, the rod 52 is rearwardly pushed out so that the operationlever 51-2 is moved in the direction of liberating the locked condition.Here, the load required for the insertion overcoming the spring is about100 g which is a value that brings about no problem compared with theload for inserting the connector or the load for holding the connector.In the case of the structure having a reduced thickness as in thepresent invention, the operation lever 51-2 is very close (in the orderof 0.1 mm) to the rotary portion of the actuator 29, and may come incontact therewith. To eliminate the probability of contact, therefore,the end of the rod 52 has been urged to be pressed onto the base 22 orthe cover 23. This makes it possible to eliminate the above-mentionedprobability of coming in contact irrespective of tolerance in size.

FIG. 68 is a front view showing in cross section a first preferredembodiment of the structure of a spindle motor that is capable ofreversely fastening the magnetic disk in the magnetic disk driveaccording to the present invention. FIG. 68 shows major portions only ofthe constituent parts to illustrate the feature in that the magneticdisk is mounted on the side of the stator coil.

Here, reference is made again to FIG. 42 to closely describe thestructure of mounting the magnetic disk 24 on the surface of the sideopposite to the stator coil 26-4 of the hub 11, thereby to clarify thedifference from FIG. 68.

In FIG. 42, first, the magnetic disk 24 that is to be locked is mountedon the outer peripheral flange portion of the hub 11. Here, since astepped portion 11' has been formed on the hub 11, the magnetic disk 24that is mounted forms a recessed portion. Next, an adhesive agent 19'such as an aerophobic adhesive agent is poured into the recessedportion, and an adhesion ring 19 is mounted on the magnetic disk 24 soas to come in contact with both the adhesive agent 19' and the uppersurface of the magnetic disk 24. Under this condition, the adhesiveagent 19' is cured so that the disk 24 is firmly secured to the hub 11.

Described below are the reasons why the adhesion ring 19 is dared to beused.

A first reason is that ever when the adhesive agent 19' is erroneouslyapplied to the surface of the magnetic disk 24, the disk surface foreffecting the reproducing/recording operations cannot be utilized.

A second reason is that the adhesion ring 19 works to prevent theadhesive agent 19' from flowing to the outer peripheral portions of themagnetic disk 24 where the magnetic head 29 exists.

A third reason is that when the adhesive agent 19' is an aerophobicadhesive agent, the adhesive agent 19' that happens to flow on thesurface of the disk does not undergo curing except under the portion ofthe adhesion ring 19 and, thus, the motion of the magnetic head 27 isnot affected.

A fourth reason is that the inner circle of the disk is adhered to thespindle hub 11, and furthermore the upper surface of the disk, theadhesion ring 19' and the spindle hub 11 are adhered together instead ofadhering the magnetic disk 24 to the flange portion of the spindle hub11. This makes it possible to precisely control the height of mountingthe magnetic disk.

The above-mentioned fastening by using the adhesion ring 19 is differentfrom the conventional push-fastening using a clamp member with respectto that the pre-load cannot be applied in the direction of holding. Thatis, in an ordinary push-fastening, a resilient member (inclusive of ascrew) is used to hold the disk 24, the resilient member havingresiliency in the direction of pushing the magnetic disk. In theadhesion-fastening using an adhesive agent of the present invention,however, the pre-load pressure cannot be applied since the adhesiveagent undergoes creeping. Because of this reason, it is important towell control the thickness at a moment when the adhesive agent is cured.

In contrast with the method of adhesion-fastening the disk 24 on thesurface of the side opposite to the stator coil 26-4 of the spindle hub11, FIG. 68 employs a method of fastening the magnetic disk on thesurface that faces the stator coil 26-4 of the spindle hub 11.

In FIG. 68, the spindle hub 11 has a flange portion 62 on the sideopposite to the stator coil 26-4, and the support surface 62a faces theside of the stator coil 26-4. Further, the spindle hub 11 has a clampmargin 63a that will fit to a damper 63 on the side of the stator coil26-4.

The flange portion 62 has a thickness t₂ which is large enough not to bewarped during the machining.

The magnetic disk 24 is supported on the support surface 62a of theflange portion 62, is clamped by a damper 63 that is forcibly insertedfrom the side of the stator coil 26-4, and is secured to the spindle hub11. The flange portion 62 has a sufficiently large rigidity, and thesupport surface 62a is formed maintaining a good dimensional precision.Therefore, the magnetic disk 24 is precisely fastened, and the recordingand reproducing operations are favorably carried out.

The clamper 63 is simply to hold the magnetic disk 24 and may have arelatively small thickness. The damper 13 is in flush with the lowersurface 11d of the spindle hub 11.

Owing to the above-mentioned structure, the height H₁₀ from the uppersurface 22i of the base 22 to the magnetic disk 24 can be decreased tobe smaller than that of the above-mentioned case of FIG. 42.

The flange portion 62 is located at a position corresponding to the armsupport portion 17 in the direction of height, and the thickness t₂ ofthe flange portion 62 is within the height H₃ of the upper half of thearm support portion 17. Therefore, the height H₁₁ between the base 21and the cover 23 corresponds to the sum (H₁₀ +H₃) he height H₁₀ and theheight H₃, and this sum can be decreased to be smaller than that of thecase of FIG. 42. It is expected that the magnetic disk drive of FIG. 68can be realized having a thickness smaller than that of FIG. 42.

In this case, furthermore, the magnetic disk 24 is arranged nearly atthe center in the direction of thickness of the housing 21 and is,hence, allowed to rotate maintaining good balance to a sufficientdegree.

FIG. 69 is a front view illustrating in cross section a second favorableembodiment of the structure of the spindle motor that is capable ofreversely fastening the magnetic disk in the magnetic disk drive of thepresent invention.

This embodiment does not employ the clamper 63 of FIG. 68 in order tofurther decrease the thickness. In FIG. 69, the portions correspondingto the constituent portions of FIG. 68 are denoted by the same referencenumerals. Here, the spindle hub 11 has substantially the sameconstruction as the spindle hub 11 of FIG. 68 except that the clampmargin 63a of FIG. 68 is eliminated. Concretely speaking, the spindlehub 11 has the flange portion 62 and the support surface 62a. Themagnetic disk 24 is fitted to the spindle hub 11, is positioned incontact with the support surface 62a, and is adhered with an adhesiveagent 61 so as to be fastened maintaining good precision.

Therefore, the height H₂₀ from the upper surface 22i of the base 22 tothe magnetic disk 24 becomes smaller than the corresponding height H₁₀of FIG. 68 by the height of the clamp margin 63a. That is, the height H₂between the base 22 and the cover 23 corresponds to the sum (H₂₀ +H₃) ofthe above-mentioned height H₂₀ and the above-mentioned height H₃, whichis smaller than the height H₁₁ of FIG. 68. Accordingly, the magneticdisk drive of FIG. 69 becomes thinner than the magnetic disk drive ofFIG. 68.

FIG. 70 is a perspective view illustrating a first favorable embodimentof the structure of the actuator in the magnetic disk drive according tothe present invention.

In FIG. 70, the arm 28 has an arm end 28-1 for holding at its end themagnetic head 27 as mentioned earlier, and is disposed to rotate in thedirection of arrow B with a second fixed shaft 45 as a center, and has aflat coil 67 attached to the rear end thereof. A pair of permanentmagnets 29-5 and 29-6 are arranged near the flat coil 67. Furthermore,an edge portion on the side of the arm 28 is curved in the direction ofwidth, and a central portion of an edge portion on the side opposite tothe above edge portion is protruded in a cornered shape to form a loweryoke 29-2 which can be arranged at the corner of the disk driveefficiently utilizing the space in the magnetic disk drive. There isfurther provided an upper yoke 29-1 of a curved shape having ordinarywidth. The upper and lower yokes 29-1 and 29-2 are magnetically coupledtogether at their both sides by using side yokes 29-3 and 29-4maintaining a predetermined distance. The flat coil 67 moves in a gapbetween the upper yoke 29-1 and the pair of permanent magnets 29-5, 29-6in a magnetic circuit 65 constituted by the above yokes, and thus adrive coil motor (DCM) is constituted.

In the actuator of this embodiment as mentioned above, the lower yoke29-2 has a broad central portion in which the magnetic flux densitybecomes great as the magnetic flux directly passes from one permanentmagnet 29-5 to the other neighboring permanent magnet 29-6 in themagnetic circuit 67. Furthermore, the sectional area is increased byincreasing the area of the lower yoke 29-2. Therefore, the problem ofmagnetic flux saturation is eliminated even when the thicknesses of thelower yoke 29-2 and the upper yoke 29-1 are decreased, making itpossible to suppress the drop in the magnetic flux density across thegap which is caused by the leakage of magnetic flux due to magnetic fluxsaturation.

The lower yoke 29-2 having the above-mentioned shape enables theactuator 29 to be installed at the corner in the magnetic disk drive toefficiently utilize the space, and the disk drive as a whole can beconstructed in a compact size.

FIG. 71, 72 and 73 are diagrams illustrating a second favorableembodiment of the structure of the actuator in the magnetic disk driveaccording to the present invention. If described in further detail, FIG.71 is a perspective view illustrating major portions of this embodiment,FIGS. 72(A) and 72(B) are a schematic plan view and a schematic frontview, and FIG. 73 is a perspective view which separately illustrates thehead assembly and the magnetic circuit.

The embodiment shown in these drawings is different from the embodimentshown in FIG. 70 with respect to that the upper yoke 29-1 has a shapethat is protruded in a cornered shape at its central portion like theshape of the above-mentioned lower yoke 29-2, the upper yoke 29-1 beingincluded in a separate magnetic circuit 66 that constitutes a drive coilmotor in combination with the flat coil 67 attached to the rear end ofthe arm 28.

Even in this embodiment, the lower yoke 29-2 and the upper yoke 29-1have broad central portions based on the same idea as the embodiment ofFIG. 70, and sectional areas are increased by increasing the areas ofthe lower yoke 29-2 and the upper yoke 29-1. Therefore, the problem ofmagnetic flux saturation does not arise despite the lower yoke 29-2 andthe upper yoke 29-1 are formed in reduced thicknesses. Accordingly, themagnetic flux density across the gap is prevented from being decreasedby the leakage of magnetic flux that stems from the magnetic fluxsaturation.

When either the upper yoke or the lower yoke has a broadened portion asin the first embodiment and when the magnet is to be adhered on eitherone of them, the yoke that has the broadened portion should be the oneon which the magnet is adhered. When the magnet is mounted on one side,in general, the magnetic flux tends to spread in the gap near the yokeof the side where there is no magnet, and the magnetic flux densityslightly decreases in the central portion of the yoke. In this case, ifthe yoke is excessively broadened, the magnetic flux spreads too broadlyand may intersect the coil in reduced amounts.

In the above-mentioned actuator structure of either the first embodimentor the second embodiment, the problem of magnetic flux saturation iseffectively overcome in the lower yoke and in the upper yoke despite thedecrease in the thicknesses of the lower yoke and the upper yokeconstituting the magnetic circuit, and the magnetic flux density acrossthe gap is suppressed from being decreased by the leakage of magneticflux that stems from the magnetic flux saturation.

Moreover, the lower yoke or both the lower yoke and the upper yoke havebroad central portions which are protruded in a cornered shape so thatthey can be arranged at a corner portion in the magnetic disk drive toefficiently utilize the space, making it possible to realize theactuator and the magnetic disk drive in compact sizes and in reducedthicknesses.

FIGS. 74 and 75 are diagrams illustrating a third favorable embodimentof the structure of the actuator in the magnetic disk drive according tothe present invention. If described in further detail, FIG. 74 is aperspective view showing a yoke portion according to the presentinvention, wherein FIG. 74(A) shows a condition where the yoke portionis disassembled, and FIG. 74(B) shows a condition where the yoke portionis assembled. FIG. 75 is a diagram illustrating in detail the headassembly that includes an actuator of the type of moving coil, whereinFIG. 75(A) is a cross-sectional front view, and FIG. 75(B) is a planview thereof.

In FIG. 74(A), the yoke portion 68 comprises an upper member 68-1 and alower member 68-2 which are bent by pressing a plate of a soft magneticmaterial having a high saturation magnetic flux density.

The upper member 68-1 has a nearly fan-shaped upper surface 68a, twoupper side surfaces 68b and 68c formed by downwardly bending both endsof the upper surface 68a at right angles, and an upper end surface 68dformed by bending the central portion of the outer circumferential edgeof the upper surface 68a at right angles. The lower member 68-2 has anearly fan-shaped lower surface 68e, two lower side surfaces 68f and 68gformed by upwardly bending both ends of the lower surface 68e at rightangles, and a protruded edge portion 68h that protrudes at the centralportion of the outer circumferential edge of the lower surface 68e. Theupper side surfaces 68b, 68c, lower side surfaces 68f, 68g, and theupper end surface 68d all have the same length. They, however, need notbe all of the same length. For instance, the upper side surfaces 68b and68c may have a length which does not downwardly protrude beyond thelower surface 68e.

Referring to FIG. 74(B), the upper member 68-1 and the lower member 68-2are disposed in a manner that the upper side surface 68b and the lowerside surface 68f as well as the upper side surface 68c and the lowerside surface 68g are overlapped intimately with each other, and the endsof the lower side surfaces 68f and 68g come in contact with the uppersurface 68a, and the end of the upper end surface 68d comes in contactwith the protruded edge portion 68h.

The upper side surfaces 68b, 68c and the lower side surfaces 68f, 68gare not in parallel with each other. Therefore, the upper side surfaces68b, 68c and the lower side surfaces 68f, 68g are overlapped upon oneanother so as to be positioned in the horizontal direction (which is inparallel with the upper surface 68a), and the lower side surfaces 68f,68g are brought into contact with the upper surface 68a so as to bepositioned in the vertical direction (in the direction of height). Theupper end surface 68d and the protruded edge portion 68h come in contactwith each other and are supported so that their attitudes arestabilized. Under the thus positioned condition, the upper surface 68aof the upper member 68-1 faces the lower surface 68e of the lower member68-2, magnetic paths MPa and MPb are formed between the upper member68-1 and the lower member 68-2 by the upper side surface 68b, lower sidesurface 68f and by the upper side surface 68c, lower side surface 68g,and an annular magnetic path MP is formed through the whole yoke portion68.

Therefore, the magnetic path MPa or MPb that had hitherto been formed bypole members which are separate parts, is now formed by the upper sidesurfaces 68b, 68c and by the lower side surfaces 68f, 68g, resulting ina reduction in the number of parts. Moreover, the magnetic paths MPa andMPb are connected at one place only, respectively, and the connectingportions have large opposing areas. Therefore, the reluctance ismaintained small at the connection portions, and is also maintainedsmall through the whole yoke portion 68. Moreover, the leakage ofmagnetic flux is reduced at the connection portions, and a high magneticflux density can be obtained at the moving portion.

In the magnetic paths MPa and MPb, furthermore, the upper side surfaces68b, 68c and the lower side surfaces 68f, 68g are overlapped upon oneanother, and have a magnetic flux density which is smaller than that ofthe upper surface 68a and the lower surface 68e. Therefore, saturationtakes place little in such portions. When a housing that accommodatesthe yoke portion 68 is made of a magnetic material and is so disposedthat a portion thereof comes in contact with the upper surface 68a orthe lower surface 68e, therefore, this contacting portion of the housingbecomes a portion of magnetic path MP of the yoke portion 68, and themagnetic flux is permitted to pass through without being saturated inthe magnetic paths MPa, MPb. Thus, the magnetic flux density can beincreased in the moving portion. Moreover, since the upper side surfaces68b, 68c and the lower side surfaces 68f, 68g are overlapped upon oneanother and the lower side surfaces 68f, 68g come in contact with theupper surface 68a, the upper member 68-1 and the lower member 68-2 areeasily positioned without the need of providing any additionalpositioning members such as dowels that were used thus far. Therefore,the parts can be machined and assembled very easily. As the upper endsurface 68d and the protruded edge portion 68h come in contact with eachother, furthermore, the attitudes of the above two members arestabilized and the reluctance can be decreased, too. In order to couplethe upper member 68-1 and the lower member 68-2 as a unitary structure,furthermore, an adhesive agent may be applied to the contacting surfacesof the upper side surfaces 68b, 68c and the lower side surfaces 68f,68g, or the two members may be held together as a unitary structure by ahousing which accommodates the yoke portion 68.

As shown in FIGS. 75(A) and 75(B), furthermore, the head assembly isconstituted by an actuator 29, an arm 28 that moves being coupled to theactuator 29, an arm end 28-1 coupled to the arm 28, and the magnetichead 27 mounted at the tip of the arm end 28-1.

The actuator 29 comprises the yoke portion 68, a magnet portion 29aconsisting of a pair of opposing permanent magnets mounted on the innersides of the upper surface 68a and the lower surface 68e of the yokeportion 68, a flat moving coil portion 29b that is movably arranged inthe magnet portion 29a, and an arm support portion 17 such as a carriagewhich rotatably supports the moving coil portion 29b and the arm 28 withthe second fixed shaft 45 as a center. The magnet portion 29a consistsof two permanent magnets having dissimilar polarities, and electriccurrents of opposite directions flowing through the opposing sides ofthe coil portion 29b receive the electromagnetic force in the samedirection due to magnetic fields of opposite directions, causing the armsupport portion 17 to be rotated.

The thus rotated arm support portion 17 comes at its rotational end intocontact with side edges 29d, 29e on the inner side of the lower sidesurfaces 68f and 68g, and thus the moving range of the actuator 29 isrestricted. That is, the side edges 29d, 29e serve as stopperscontributing to simplifying the structure of the actuator 29. In theactuator 29, since the yoke portion 68 has a small reluctance and a highsaturation magnetic flux density, a high magnetic flux density isobtained across the permanent magnets (high magnetic flux density in themoving portion) and a large force acts on the coil 29b. Therefore,despite of its small size, the actuator 29 produces a large torque andcan be favorably employed for a compact and thin magnetic disk drivesuch as the card-type magnetic disk drive.

In the above embodiment, the upper side surfaces 68b, 68c are on theouter side of the lower side surfaces 68f, 68g, and the positioning inthe vertical direction (height direction) is accomplished by the ends ofthe lower side surfaces 68f and 68g. However, a relation in position maybe reversed between the upper side surfaces 68b, 68c and the lower sidesurfaces 68f, 68g. Moreover, the cover 22 may be constituted by using amagnetic material and may be used as a portion of the magnetic circuitthat is formed by the actuator 29.

FIG. 76 is a perspective view illustrating in a disassembled manner ayoke 168a in the structure of the actuator according to a fourthpreferred embodiment of the present invention, and wherein the portionshaving the same functions as the portions of FIG. 74 are denoted by thesame reference numerals but are not described here again or describedonly briefly.

In the yoke portion 168 of FIG. 76, the upper side surfaces 168b, 168cand the lower side surfaces 168f, 168g have widths which are nearlyone-half the lengths of the sides of the upper surface 68a and the lowersurface 68e.

Thus, the yoke portion 168 has a small shape and occupies a reducedvolume, enabling other mechanical parts to be arranged in the portionprovided by the reduction in the widths of the upper side surfaces 168b,168c and the lower side surfaces 168f, 168g, making it possible torealize the magnetic disk drive in a further decreased size. In thiscase, the upper side surfaces 168b, 168c and the lower side surfaces168f, 168g have decreased widths but have thicknesses which are twice asgreat as those of the upper surface 68a and the lower surface 68e.Therefore, the magnetic saturation does not take place in the upper sidesurfaces 168b, 168c and in the lower side surfaces 168f, 168g so far asthe housing is not used as the magnetic path.

FIG. 77 is a perspective view showing lower members 69-2a to 69-2c onlyof the yoke portions 69a to 69c in the structure of the actuatoraccording to a further embodiment of the present invention, and whereinthe portions having the same functions as the portions explained withreference to FIG. 74 are denoted by the same reference numerals but arenot described here again or described only briefly.

As shown in FIG. 77(A), the lower member 69-2a of the yoke portion 69ahas a lower end surface 68k that is formed continuously to the lowerside surfaces 68f, 68g and to the lower surface 68e. The lower endsurface 68k serves as a portion of the magnetic path and supports theupper member to stabilize its attitude.

The lower member 69-2b of the yoke portion 69b shown in FIG. 77(B) hastwo lower end surfaces 68l and 68m formed from the lower surface 68e.The lower end surfaces 68l and 68m serve as portions of the magneticpath and support the upper member.

The lower member 69-2c of the yoke portion 69c shown in FIG. 77(C) has alower end surface 68n that works as a stopper and that is formed fromthe lower surface 68e on the inside of the lower side surface 68f. Thelower end surface 68n restricts the moving range of the actuator 29instead of the above-mentioned side edge 29d, and serves as a portion ofthe magnetic path.

The upper members of the yoke portions 69a to 69c are symmetrical to thelower members 69-2a to 69-2c; i.e., they fit together so that the lowerside surfaces 68f, 68g, and the lower end surfaces 68k, 68l, 68m, 68nare overlapped upon one another. Or, the upper members of the yokeportions 69a to 69c may be so formed as to simply have the upper surface68a and the upper side surfaces 68b, 68c.

In the aforementioned embodiment, either one of the upper member 68-1 orthe lower member 68-2 may be on the upper side and the other one may beon the lower side. The upper member 68-1 and the lower member 68-2 canbe prepared by various methods in addition to pressing. Only onepermanent magnet may be used for the magnet portion 29a.

According to the present invention, the yoke is constituted using areduced number of parts, and the reluctance is lowered to obtain a highmagnetic flux density at the moving part. Moreover, the upper member andthe lower member are easily positioned to facilitate the assembling.

FIGS. 78, 79, 80 and 81 are diagrams illustrating an embodiment which isan improvement from the first preferred embodiment of the wholestructure of the spindle motor shown in FIG. 50. If described in furtherdetail, FIG. 78 is a sectional view of the spindle motor of the axialflux type according to the above improved example. Aventurine portions75 denote a magnetic path auxiliary means which according to thisembodiment is formed together with a rotor yoke 76 as a unitarystructure.

FIGS. 79 to 81 illustrate in detail the structure of the spindle motorof the axial flux type according to the present invention, wherein FIG.79 is a perspective view of a constituent block, FIG. 80 is a sectionalview along the line IV--IV of the constituent block of FIG. 79, and FIG.81 is a sectional view along the line V--V of the constituent block ofFIG. 79. Aventurine portions 75 denote a magnetic path auxiliary meanswhich according to this embodiment is formed together with the rotoryoke 76 as a unitary structure.

In FIG. 79, an annular magnetic path auxiliary means 75 made of amagnetic material is disposed at a position near the magnet 26-3 and thestator 26-4 to trap the leakage magnetic flux. That is, the annularmagnetic path auxiliary means 75 is formed together with the rotor yoke76 as a unitary structure so as to include therein the magnets 26-3 andstator coils 26-4 that are annularly arranged. The gap between themagnetic path auxiliary means 75 and the stator yoke 77 is set to besmaller than the gap between the magnets 26-3 and the stator yoke 77.When the spindle motor 26 is rotating, therefore, a closed magnetic pathis formed in the circumferential direction as indicated by a broken linewith arrow in FIG. 80. As shown in FIG. 81, furthermore, the leakagemagnetic flux is trapped by the magnetic path auxiliary means 75 whichexhibits properties of the magnetic material, and auxiliary closedmagnetic paths are formed in the radial direction passing through themagnetic path auxiliary means 75. That is, when there is no magneticpath auxiliary means, the magnetic flux passes through the closedmagnetic path of the circumferential direction only. In this embodiment,however, the magnetic flux disperses in the auxiliary closed magneticpaths of the radial direction. Therefore, the magnetic flux densitydecreases in the rotor yoke 76 and in the stator yoke 77; i.e., themagnetic flux is not saturated in the rotor yoke 76 and in the statoryoke 77, resulting in a decrease in the leakage magnetic flux density.On the other hand, the magnetic flux density increases across the gapfor rotating the rotor yoke 76 compared with that of when there is nomagnetic path auxiliary means.

Therefore, even when the rotor yoke 76 and the stator yoke 77 aremachined to have thicknesses smaller than those of the prior art, theelectric current flowing into the stator coils 26-4 can be efficientlyconverted into a torque. At the same time, the magnetic head, recordingdisk and like portions that deal with recording signals are lessaffected by the leakage magnetic flux density.

FIG. 82 is a sectional view illustrating another embodiment which is animprovement from the first preferred embodiment of the whole structureof the spindle motor of FIG. 50, and wherein the same constituentportions as those of FIG. 78 are denoted by the same reference numeralsbut are not described. In this embodiment, the magnetic path auxiliarymeans 75 is formed integrally with the stator yoke 77. Even thisconstitution makes it possible to obtain the same effects as those ofthe embodiment of FIGS. 78 to 81.

In addition to the above, though not diagramed, the magnetic pathauxiliary means 75 may be split and are formed integrally with the rotoryoke 76 and the stator yoke 77, and the thus split magnetic pathauxiliary means 75 are opposed to each other to obtain the same effects.

In FIGS. 78 and 82, the magnetic path auxiliary means 75 is arranged soas to include the magnet 26-3 consisting of a plurality of magnetelements and the stator 26-4 consisting of a plurality of coil elementsthat are annularly and contiguously arranged from both the inner andouter peripheral sides. However, the leakage magnetic flux density canbe decreased to be smaller than that of the prior art even when themagnetic path auxiliary means 75 is arranged on either the innerperipheral side or the outer peripheral side only.

According to the above improved embodiments shown in FIGS. 78 to 82, themagnetic path auxiliary means helps decrease the leakage magnetic fluxdensity that is caused by saturation in the rotor yoke and in the statoryoke, and the electric current flowing into the coil is efficientlyconverted into a torque and, besides, the portions such as the magnetichead and the recording disk that deal with recording signals are lessaffected by the leakage magnetic flux density. It is therefore allowedto easily provide a spindle motor having a size and a thickness whichare smaller than those of the prior art.

FIGS. 83 and 84 are diagrams illustrating a preferred embodiment of amagnetic head retracting assembly in the magnetic disk drive of thepresent invention. If described in further detail, FIG. 83 is a planview which illustrates a portion of the magnetic head retractingassembly in an emphasizing manner, and FIG. 84 is a side view whichschematically illustrates the magnetic head retracting assembly.

The magnetic disk drive and the IC memory card used for personalcomputers require a high degree of durability with respect to not onlyshocks but also external magnetic field. The IC cards must not permitdata to become abnormal even in a magnetic field which is as intense asone kilogausses. However, equipment having an aluminum base/cover arenot generally capable of withstanding such an intense magnetic field. Inthe magnetic disk drives, in general, the magnetic head and the mediumportion (magnetic disk) must be placed in a magnetic field which isweaker than 5 gausses.

According to the present invention, therefore, a steel base/cover isemployed as mentioned earlier to completely shield the magnetism. Asteel plate having a thickness of about 0.4 mm exhibits a shieldingeffect to a degree sufficient to meet the above demand. However, theproblem exists in that the steel plate that is press-worked often has aresidual magnetization of as great as about several tens of gausses. Asrequired, therefore, the magnetic annealing is effected to cope with theproblem.

To minimize the effect caused by the external magnetic field, it isimportant that the magnetic head is retracted to the data zone when thepower source is turned off. This is because, the magnetic head has alarge effect for concentrating the magnetic flux and just under themagnetic head, the data is affected by a magnetic field of the order of10 gausses and is likely to be erased in a magnetic field of the orderof 100 gausses. In the disk medium without the magnetic head, on theother hand, the data is not erased even in a magnetic field which is asstrong as about 1000 gausses. In view of the fact that a portable diskis affected by the magnetic field disturbance particularly when it isbeing carried, it is essential to employ a mechanical retractingassembly which does not rely upon the VCM (voice coil motor) drive.

In a magnetic disk drive having a floating magnetic head, in particular,it is essential to provide a magnetic head retracting assembly whichretracts the magnetic head to the parking zone when the disk is stoppedin order to avoid damage to the data zone during the CSS (contact startstop) operation, and an actuator locking assembly for holding theretracted magnetic head. Even in the magnetic disk drive using anegative-pressure slider (zero-load slider) that does not perform theCSS operation, it is necessary to employ the retracting and lockingoperations in view of the fact that the magnetic head comes intocollision with the medium when a shock is imparted thereto from theexternal side. Moreover, the magnetic disk drive having the unloadingmechanism requires a mechanism which reliably moves the magnetic head tothe unloading position and holds it at that position when the powersource is cut off.

Usually, the magnetic head retracting assembly:

(1) utilizes a return spring,

(2) utilizes a counter electromotive force of the spindle motor toretract the actuator, or

(3) utilizes the gravity.

Further, the actuator locking assembly:

(1) utilizes a ratchet mechanism,

(2) utilizes the frictional force, or

(3) utilizes the magnetic force.

So far as a linear spring is used, however, the return spring in theordinary magnetic head retracting assembly (1) exhibits a change in theoffset force depending upon a position on the data zone, and greatlyaffects the control system. Moreover, an excessively great offset forceis applied at a position opposite to the retracted zone, and becomes acause of an increase in the consumption of electric power. Even in thecase of the retracting assembly (2), the electromotive force of thespindle motor decreases with a decrease in the size of the magnetic diskdrive, and a sufficiently large retracting force is not obtained.Furthermore, the magnetic head retracting assembly (3) which utilizesthe gravity is not applicable to the balanced rotary actuator whichnowadays is chiefly used. In the modern small disk drives, furthermore,it is not allowed to determine the direction of installation, and theassembly (3) is not utilizable.

Further, the actuator locking assembly (1) requires a solenoid or thelike for liberating or holding the actuator. The actuator lockingassembly (2) requires a fine and cumbersome setting. Even in the case ofthe locking assembly (3) which performs the so-called catching using themagnetic force of a magnet, the effective range is limited to near theparking zone. The retracting assembly which uses the return spring hasthe locking ability, but its locking force is weaker than the retractingforce unless a magnetic spring is used, and is not practicable.

The present invention therefore employs a retracting assembly by using amagnet as shown in FIGS. 83 and 84. Here, the head assembly has a rotaryactuator 29 (see, for example, FIG. 70), and has a retraction magnet 85at the outer edge of a flat coil 86 of the actuator 29 in order tomaintain the magnetic head 29 under the retracted condition. Moreover,retraction yokes 87 are arranged under and over the retraction magnet 85thereby to form a closed magnetic path.

If concretely described with reference to a graph of FIG. 85 and a gapchanging structure of FIG. 86, a gap G in the magnetic circuit is so setin the data zone that a gap value g will vary in proportion to aninverse number of a value X+X₀ which is obtained by adding a givenintegration constant X₀ to a moving distance X of the magnetic head.Moreover, a stepped portion 87-1 is formed in the yoke 87 so that thegap value g will abruptly decrease in the locking zone. With thisformation, a constant torque is produced in the data zone which isgreater than the static friction of the bearing means 46. In the lockingzone on the outer portion of the magnetic disk, on the other hand, thetorque suddenly increases. Therefore, a large holding torque is obtainedand the magnetic head is reliably locked.

FIG. 87 is a diagram showing a model of magnetic circuit for explainingthe principle of the magnetic head retracting assembly according to thepresent invention.

Generally, there are various methods for calculating magneticattraction, and a method which uses a change ratio of magnetic energyand is used most conveniently will be hereby explained.

Magnetic energy W of a system expressed by magnetomotive force NI,magnetic flux θ and magnetic resistance R is given by:

    W=1/2φ.sup.2 R=1/2NIθ=1/2(NI).sup.2 /R

The force generated is given as follows by differentiating magneticenergy in the moving direction:

    F=dW/dx=-1/2(NI).sup.2 /R.sup.2 dR/dx=-1/2θ.sup.2 dR/dx

Let's consider a magnetic circuit model such as one shown in FIG. 87. Inthis case, magnetic energy is stored in the space, the magnet and theyoke. Here,

lg: air gap distance (inclusive of thickness of magnet; g is a suffix)

lm: thickness of magnet (m is a suffix)

S': sectional area of magnet

μo: permeability in air

μr: permeability of recoil

He: intersection of tangent of demagnetization curve at operating pointwith B=0 (linearized coercive force)

Br: intersection of tangent of demagnetization curve at operating pointwith H=0 (linearized residual magnetic flux density; Br=μrHe)

Assuming in this case that the magnetic resistance inside the yoke canbe neglected (or the magnetic energy does not exist), the magneticresistance R of this magnetic circuit can be expressed as follows:##EQU1## If μo=μr in this case, R=lg/(μo S')

On the other hand, the magnetomotive force NI is given as follows:

    NI=He lm

Therefore, assuming that the area S' does not change,

    φ=NI/R=μ.sub.0 S'H.sub.e lm/lg

    dR/dx=1/(μ.sub.0 S')dlg/dx

Accordingly, the generated force can be given as follows: ##EQU2##(generated force of gap change)

As can be understood from the above explanation, a large generated forcecan be obtained when the magnet is thick relative to the gap and the gapchange ratio is great. To obtain predetermined force irrespective of theposition X, ##EQU3## x₀ : integration constant Since it is practicallydifficult to produce the shape having such functions, a substantiallyconstant torque can be obtained even by a linear change if the gapdistance lg is made sufficiently greater than the thickness lm of themagnet.

When the device is used as the lock, a step or steps may be provided sothat this gap change becomes sufficiently great.

FIG. 88 is a graph showing the actually measured result of the torque inthe gap change type head retraction mechanism. According to the actuallymeasured result, a substantially constant retraction force can beobtained throughout the full stroke of the head 27, and a torque aboutfour to nine times the retraction force is generated at the lockposition on the right side of the graph, so that sufficient performanceas the lock mechanism can also be obtained. The holding torque at thislock position becomes greater with a greater thickness (lm) of themagnet 87 as can be appreciated clearly from the actually measuredresult of FIG. 88 and from the magnetic circuit model of FIG. 87.

FIG. 89 is a perspective view of an example of the area change typeretraction mechanism. In FIG. 89, the overlapping area of thepositioning magnet 85 and the positioning yoke 87 is change inside theplane between them in the direction in which the magnetic head 29under-goes displacement, so as to retract the head 29. More inparticular, the overlapping area between the magnet 85 and the yoke 87becomes progressively greater linear-function-wise towards the rightside, and the width of the yoke 28 is drastically increased by forminganother step 87-2 with respect to the planar direction of the yoke 87.With such a construction, the change with respect to the moving distanceX of the retraction force can be calculated using the magnetic circuitmodel shown in FIG. 87. Namely, this calculation provides:

    dR/dx=-lg/(μo S.sup.2)dS/dx

Accordingly, the generated force is given as: ##EQU4## (generated forceof area change)

In other words, a predetermined force can be obtained by the linearchange of the area S.

In the lock area, a step portion is disposed in the same way as in FIG.85 so that the holding torque is increased and the magnetic head can belocked reliably.

FIG. 90 shows another example of the retraction mechanism for themagnetic head in the magnetic disk drive according to the presentinvention.

In this example, the magnet 85 is not disposed at the moving portion butthe magnet 85 as the permanent magnet is assembled in a part of the yoke87 at the fixed portion. An iron plate as a soft magnetic substance isdisposed at the moving portion. This arrangement provides the effectsimilar to that of other embodiments. In this example, however, amagnetic circuit other than the gap is likely to be formed and in such acase, a part of the magnetic flux generated by the permanent magnet doesnot contribute to the generation of the retracting force. For thisreason, the design of the magnetic circuit becomes more difficult. Inthis embodiment, the yoke 87 is made of a sheet metal which issubstantially concentric with the center of rotation, and the centershape and other groove shapes are finished to predetermined shapes.

In any of the examples of the head retracting mechanism and the lockmechanism according to the present invention, the retracting force whichis substantially constant throughout the full regions of the magneticdisk can be generated by the simple mechanism and a sufficiently largelock force can be generated at the lock position. Accordingly, a compactand high reliability magnetic disk drive can be accomplished. In theseembodiments, the direction of the magnetic flux exists in the axialdirection of the actuator pivot, but can be set in the radial direction.

FIG. 91 is an exploded perspective view showing an example of thehousing constituted by three different elements. Since the constituentelements other than those of the housing in the embodiment shown in FIG.91 are substantially the same as those of many other embodiments, theportions other than the housing will be omitted.

Here, the housing of the magnetic disk drive comprises a flat sheet-likebase portion 122 at a lower portion, a cover portion 123 on the flatsheet at an upper portion and a frame portion 121 disposed at the sideportions. The thickness of this frame portion 121 is set in advance sothat the disk, the disk drive unit, the head assembly, and so forth, canbe accommodated inside the housing.

If the base portion 122 and the cover portion 123 are made of an irontype metal having higher rigidity than aluminum, the thickness of eachof the base portion 122 and the cover portion 123 can be reduced.Furthermore, if a magnetic material among the iron type metals is used,it can be used also as the yoke member for the actuator motor, and thethickness of the apparatus can be further reduced as a whole. Thematerial of the frame portion 122 disposed in such a manner as to besandwiched between the base portion 122 and the cover portion 123 isaluminum, for example, because die casting which can be practiced can beutilized.

When the magnetic substance is used for the base portion 122 and thecover portion 123, they can also be used as the yokes of the spindlemotor and actuator motor or as auxiliary yokes. They also have themagnetic shielding effect. When the material of the frame portion 121 isa magnetic substance inclusive of iron, etc., there can be obtained theadvantage that the magnetic shielding effect can be improved much morethan when only the base portion 122 and the cover portion 123 are madeof the magnetic material.

FIGS. 92, 93, 94 and 95 show most preferable embodiment of the diskdrive having the overall structure wherein one disk and two heads areassembled in the housing according to the present invention. FIG. 92 isa sectional front view of the overall structure, FIG. 93 is aperspective view showing the principal portions of the overallstructure, FIG. 94 is an exploded perspective view showing variouscomponents which are under the exploded state.

As shown in these drawings, the disk drive comprises one disk having adiameter of equal to or less than 1.89 inches, a disk driving means forrotating the disk, two magnetic heads capable of read and write from andto the surface of the disk, arms for supporting the magnetic heads, anactuator carriage for rotatably supporting the arms, bearings forallowing the rotation of the actuator carriage, a positioner drivingmeans for rotating the actuator carriage and moving the magnetic headsto predetermined positions on the surface of the disk as a recordingmedium, a base and a cover mating with each other to form a housing(which protects at least a disk enclosure portion, the disk drivingmeans, the magnetic heads, the actuator carriage, the bearings and theactuator driving means), and a circuit for controlling at least the diskdriving means, the magnetic heads, and the read/write operation by theactuator driving means.

In this case, the circuit described above comprises a flexible printedcircuit board, the height of the magnetic disk drive is about 5 mmaccording to Type II of PCMCIA.

More in particular, reference numeral 211 in FIGS. 92 to 95 denotes thecover, and reference numeral 212 does the cover. Reference numerals 213aand 213b denote a disk side fixed shaft and an actuator side fixedshaft, respectively. As seen from FIG. 32, the base 211 and the cover212 are made of an iron type metal, and such a metal provides, asmentioned earlier, a high magnetic shielding effect. The fixed shafts213a and 213b are realized by using the shafts shown in FIG. 42, and thelower ends having flanges are fixed to the base 211 by riveting (orpress fitting and welding).

Furthermore, the upper end of each fixed shaft 213a, 213b is fixed tothe cover 212 with the structure shown in FIG. 46.

One magnetic recording medium (disk) 222 is rotatably held, via abearing and a spindle hub, on the shaft 213a, and a spindle motor 220 isassembled. An actuator 230 inclusive of the magnetic head 232 and thearm 238 is rotatably in a predetermined range of angle held on theactuator side fixed shaft 213b. This actuator 230 can move, as mentionedbefore, the magnetic head 232 to a desired track on the disk 222 and cankeep it positioned there.

Reference numeral 251 denotes a flexible circuit board. This singleflexible circuit board 251 is bonded and fixed, as mentioned in detailin FIG. 6, to the inner surface of the base 211 and cover 212 by asuitable adhesive, or the like. A group of electronic circuit components216 necessary for controlling the operations of the disk drive as awhole (such as a servo circuit, a spindle motor control circuit, aread/write circuit, an interface circuit, etc.) are assembled andmounted on the printed circuit board 251 by dividing into an analoggroup circuit and digital group circuit. Furthermore, the printedcircuit board 251 is connected to connectors 217 which are supported bythe base 211 and the cover 212. When the connectors are connected to aplug portion of an external electronic appliance (such as a portablenote-type personal computer), the magnetic disk drive shown in FIGS. 92to 95 functions as an external memory device for the external electronicappliance.

Preferably, the spindle motor 220 in these drawings is a flat coil typeDCM having an axial gap. Its hub 221 supports the disk 222 by bonding. Amagnet 224 is bonded inside the spindle hub 221 by bonding. This magnet224 is disposed in parallel with the disk 222 and is subjected tomultipolar magnetization in a perpendicular direction. The spindle hub222 functions as the yoke for the magnet 224.

Reference numeral 227a denotes a upper bearing of the disk, and 227bdoes its lower bearing. Reference numeral 228 denotes a spacer forsecuring a predetermined gap between the upper bearing 227a and thelower bearing 227b. The inner races of the lower and upper bearings arebonded and fixed to the fixed shaft 213a. The spindle hub 221 is made ofan iron type material. The inner peripheral portion of the spindle hub221 is bonded to the outer races of the upper and lower bearings 227aand 227b. A plurality of coils 225 are disposed below the magnet 224,and each of these coils is shaped concentrically on a flexible substrateand is disposed equidistantly with respect to the others. The magneticcircuit of the brushless motor described above is constituted by thespindle hub 221, the magnet 224, the coils 225 and the base 211. Eachlead wire (not shown in FIGS. 92 to 95) extended from each coil 225 isconnected to a corresponding terminal on the printed circuit board 251,and a current for driving the spindle motor 220 is supplied to each coil225 through each lead wire. When a current is supplied to each coil 225,a driving force is generated inside the magnetic circuit described aboveand rotates the hub 221.

The structure of the actuator 230 inclusive of the magnetic heads 232and the arms 238 will be explained in further detail. Reference numeral225a denotes a back bearing of the actuator 230 and reference numeral225b does its upper bearing. Reference numeral 236 denotes a spacer forsecuring a predetermined gap between the upper bearing 235a and thelower bearing 235b. The inner races of the upper and lower bearings235a, 235b are bonded and fixed to the fixed shaft 213b. Referencenumeral 231 denotes a block made of an iron type material. The innerperipheral portion of the block 231 is bonded to the outer races of thelower and lower bearings 235a, 235b.

Furthermore, the arms 238 are coupled to the block 231 from an axialdirection by laser spot welding. Each magnetic head 232 is bonded andfixed to one of the ends of each arm 238. These two magnetic heads 232face both surfaces of the magnetic recording medium 222, respectively.The coils 233 for driving the actuator 230 are disposed on the oppositeside to the arms 238 and are fixed to the block 231 by resin molding.

Reference numeral 234 denotes a flexible printed board, which functionsas a signal line for transferring read/write signals between themagnetic heads 232 and the control circuit and a feeder for supplyingcurrent to the coil of the actuator. This flexible printed board 234 isconnected to the flexible printed circuit board 251 on the opposite sideto the magnetic heads 232 by soldering.

A VCM (Voice Coil Motor) shown in FIG. 71 provides a driving forcenecessary for moving each magnetic head 232 to a desired position on thedisk. This VCM comprises upper and lower yokes 242, side surface yokes243a, 243b and a magnet 244 that together form a magnetic circuit 240,and each coil 233 disposed in this magnetic circuit 240. When a currentis allowed to flow through each coil 233, the actuator 230 startsrotating.

In this case, a contact type integral magnetic head for verticalmagnetic recording, disclosed in a unexamined Japanese patentpublication 3-178017, is utilized for the magnetic head 232 so that thedisk drive becomes light weight and can be driven by low voltage.However, by employing a loading/unloading mechanism, the ordinarymagnetic head which effects horizontal recording and is equipped with ahead slider having a predetermined float quantity, can also be used inplace of the integral magnetic head described above.

According to such a structure, there occurs ordinarily the space whichcannot be occupied at the upper and lower end portions of the housingwith the exception of the proximity of the shaft and the actuator.

For this reason, various circuits can be assembled into the spacedescribed above, so that the space can be utilized more effectivelyinside the housing.

In another embodiment shown in FIGS. 92 to 95, the outer dimension ofthe disk drive is in agreement with the size of the specification of ICmemory cards in accordance with the standard specification of PCMCIA orJEIDA. Furthermore, the connector of this disk drive can be made equalto the connector of the IC memory cards by using a magnetic recordingmedium (disk) having a diameter of about 1.3 in. (up to 1.89 in.), andthe size can also be made equal to that of the IC memory cards. Further,if the same specification of an interface is adopted, it becomespossible to realize a compatibility with the IC memory card.

After all, according to 1-disk magnetic disk drive of the presentinvention, its memory capacity can be increased to at least 40M byteswhile keeping its height equal to or less than 8 mm.

We claim:
 1. A disk drive for insertion into a slot formed in anexternal apparatus, said slot having a size for receiving an IC memorycard therein, said disk drive comprising:a housing; and at least oneconnector fixed outside said housing; wherein an inside of said housingincludesa) a disk that stores information; b) a disk driving means thatforces said disk to rotate; c) a head assembly that performs read/writeoperations on said disk; and d) electronic circuitry that includes atleast one interface circuit, said at least one interface circuit allowscommunication with an external host computer formed in said externalapparatus, said electronic circuitry mounted on a printed circuit board,wherein said at least one connector is connected to said electroniccircuitry, wherein said at least one interface circuit is coupled tosaid external host computer via said at least one connector such thatsaid external host computer receives information from said at least oneinterface circuit and sends information thereto, and wherein a wholeouter dimensions of said housing and said at least one connector havinga thickness of 5 mm which is compatible in size with a size of the ICmemory card specified by a specification of type II of PCMCIA, whereinsaid housing comprises a base at the lower side and a cover at the upperside, and wherein said printed circuit board includes at leastelectronic components that constitute said electronic circuitry, saidprinted circuit board being located along either one inner wall surfaceor both respective inner wall surfaces of said base and said cover,wherein said electronic components are separated into one groupprocessing at least analog signals and another group processing onlydigital signals, and wherein the former group is mounted on either oneof upper and lower sides of said printed circuit board, while the lattergroup is mounted on the other of the upper side and lower side thereof,separately to each other.
 2. A disk drive as set forth in claim 1,wherein said electronic circuitry at least includes:a read/write circuitthat receives read signals from said head assembly and provides writesignals to said head assembly; and, a control circuit that controls theoperations of said disk driving means and said head assembly.
 3. A diskdrive as set forth in claim 1, wherein said head assembly at leastincludes:a head for reading to and/or writing from a predeterminedposition on said disk; an arm that supports said head; and, a rotarytype actuator that forces said arm to rotate in either direction andsaid head to move to said predetermined position on said disk.
 4. A diskdrive as set forth in claim 1, wherein constituent parts that include atleast said disk, said disk driving means, said head assembly and theelectronic circuitry inside said housing are driven on a power supply of3 to 3.5 volts.
 5. A disk drive as set forth in claim 1, wherein saidhousing maintains a tightly closed condition with the exception ofventilation through an air filter.
 6. A disk drive as set forth in claim1, wherein said housing has a rectangular form.
 7. A disk drive as setforth in claim 6, wherein it has outer dimensions in plane directions ofapproximately 85.6 mm×54 mm.
 8. A disk drive as set forth in claim 6,wherein said connector is attached to a portion of the sides havingshorter dimensions of said housing.
 9. A disk drive as set forth inclaim 8, wherein said connector is located in either one side havingshorter dimensions of said housing.
 10. A disk drive as set forth inclaim 9, wherein only one connector is provided as said connector.
 11. Adisk drive as set forth in claim 9, wherein said connector is attachedto either one side with shorter dimensions of said housing, said sidebeing in a position opposite to said head assembly across said disk. 12.A disk drive as set forth in claim 1, wherein said printed circuit boardis composed of a flexible printed circuit board which is bent into alower portion and an upper portion coupled with each other, in a formsuch that said disk is put between said lower portion and upper portionof said flexible printed circuit board.
 13. A disk drive as set forth inclaim 12, wherein a bent portion of said flexible printed circuit boardare formed in the longer side of said housing.
 14. A disk drive as setforth in claim 13, wherein the upper and lower sides of said flexibleprinted circuit board are connected by means of two connecting portions,and wherein said connecting portions are constructed to be bent back.15. A disk drive as set forth in claim 14, wherein each of saidconnecting portions have excess length, which is bent back so that saidexcess length protrudes inside said housing.
 16. A disk drive as setforth in claim 1, wherein both of said base and said cover are made ofmetal, and are metal based printed circuit boards also used as saidprinted circuit board, respectively.
 17. A disk drive as set forth inclaim 1, wherein said connector is connected to said group processingonly digital signals.
 18. A disk drive as set forth in claim 1, whereinsaid electronic components are located between said printed circuitboard and said base and between said printed circuit board and saidcover, and said electronic components are located at the respectiveinner wall surfaces of said base (22) and said cover (23).
 19. A diskdrive as set forth in claim 18, wherein on one surface of said printedcircuit board are formed predetermined circuit patterns for assemblingsaid electronic components, while on the other surface of said printedcircuit board are formed ground patterns for electrically shielding saidelectronic components, and wherein said circuit patterns are located soas to face the inner wall surfaces of said base and said cover.
 20. Adisk drive as set forth in claim 1 wherein said printed circuit board iscomposed of a first printed board element and a second printed boardelement that are located separately each other along the respectivelycorresponding inner wall surfaces of said base and said cover, andwherein said first printed board element, having at least one firsttongue portion in which a first group of terminals are formed, isincluded in said base, said first tongue portion being projected at afirst fringe portion of said base, wherein said second printed boardelement, having at least one second tongue portion in which a secondgroup of terminals are formed, is included in said cover, said secondtongue portion being projected at a second fringe portion of said cover,and wherein said first tongue portion and said second tongue portion areconstructed such that they are fixed together by means of anisotropicconductive adhesive, said first group of terminals and the correspondingsecond group of terminals facing each other.
 21. A disk drive as setforth in claim 20, wherein said first fringe portion of said base andsaid second fringe portion of said cover are also fixed together bymeans of said anisotropic conductive adhesive.
 22. A disk drive as setforth in claim 20, wherein said first printed board element have aplurality of first tongue portions and said second printed board elementhave a plurality of second tongue portions, said first and second tongueportions being projected toward plural sides of said first fringeportion of said base and toward plural sides of said second fringeportion of said cover, respectively.
 23. A disk drive as set forth inclaim 1, wherein it has a thickness of less than 8 mm.
 24. A disk driveas set forth in claim 1, wherein it has a thickness of approximately 5mm.
 25. A disk drive as set forth in claim 1, wherein a plurality ofinsertion guide portions, which allow said housing to be inserted into aslot of a host device, are constructed so that a thickness of each offringe portions of said housing in the direction of longer side thereofbecomes smaller than the whole thickness of said housing, and whereininsertion guides for inserting said housing into a slot of an externalhost device are formed by said insertion guide portions.
 26. A diskdrive as set forth in claim 1, wherein, in the remaining space withinsaid housing other than a movable space where at least said disk, saiddisk driving means and said head assembly can be moved, a filler havinga form corresponding to said remaining space is placed in said remainingspace.
 27. A disk drive as set forth in claim 26, wherein said filler ismade of resin material.
 28. A disk drive as set forth in claim 26,wherein said filler includes conductive material inside said filler. 29.A disk drive for insertion into a slot formed in an external apparatus,said slot having a size for receiving an IC memory card therein, saiddisk drive comprising:a housing; and at least one connector fixedoutside said housing, said at least one connector being specified by aspecification of PCMCIA-ATA, wherein an inside of said housingincludesa) a disk that stores information; b) a disk driving means thatforces said disk to rotate; c) a head assembly that performs read/writeoperation on said disk; and d) electronic circuitry that includes atleast one interface circuit, wherein said at least one connector isconnected to said electronic circuitry, and wherein a whole outerdimensions including said housing and connector are a same in size asthose of the IC memory card standardized by a specification of type IIof PCMCIA having a thickness of 5 mm, wherein said housing comprises abase at the lower side and a cover at the upper side, and wherein aprinted circuit board includes at least electronic components thatconstitute said electronic circuitry, said printed circuit board beinglocated along either one inner wall surface or both respective innerwall surfaces of said base and said cover, wherein said electroniccomponents are separated into one group processing at least analogsignals and another group processing only digital signals, and whereinthe former group is mounted on either one of upper and lower sides ofsaid printed circuit board, while the latter group is mounted on theother of the upper side and lower side thereof, separately to eachother.
 30. A disk drive for insertion into a slot formed in an externalapparatus, said slot having a size for receiving an IC memory cardtherein, said disk drive comprising:a housing; and at least oneconnector fixed outside said housing; wherein an inside of said housingincludesa) at least one disk that stores information; b) a disk drivingmeans that forces said at least one disk to rotate; c) a head assemblythat performs read/write operations on said at least one disk; and d)electronic circuitry that includes at least one interface circuit, andwherein said at least one connector is connected to said electroniccircuitry, wherein said housing hasa base element located at a bottomportion of said housing; a cover element located at a top portion ofsaid housing; and a frame element that is located at a side portion ofsaid housing and has a predetermined thickness, and wherein a wholeouter dimensions including said housing and said at least one connectorhaving a thickness of 5 mm which is compatible in size with a size ofthe IC memory card specified by a specification of type II of PCMCIA,wherein a printed circuit board includes at least electronic componentsthat constitute said electronic circuitry, said printed circuit boardbeing located along either one inner wall surface or both respectiveinner wall surfaces of said base element and said cover element, whereinsaid electronic components are separated into one group processing atleast analog signals and another group processing only digital signals,and wherein the former group is mounted on either one of upper and lowersides of said printed circuit board, while the latter group is mountedon the other of the upper side and lower side thereof, separately toeach other.
 31. A disk drive as set forth in claim 30, wherein said baseand said cover are made of metal.
 32. A disk drive for insertion into aslot formed in an external apparatus, said slot having a size forreceiving an IC memory card therein, said disk drive comprising:ahousing, an inside of said housing includesa disk that storesinformation; a disk driving means that forces said disk to rotate andthat includes a motor having a stator in a position inside an outerdiameter of said disk; a head assembly that performs read/writeoperations on said disk; and electronic circuitry that includes at leastone interface circuit which allows communication with an external hostcomputer formed in said external apparatus; and at least one connector,that is connected to said electronic circuitry, is fixed outside saidhousing, wherein said interface circuit is coupled to another connectorof said external host computer via said at least one connector which isconnected to said electronic circuitry, so as to receive informationfrom said interface circuit and send information to said interfacecircuit, and wherein a whole outer dimensions including said housing andsaid at least one connector having a thickness of 5 mm which iscompatible in size with a size of the IC memory card specified by aspecification of type II of PCMCIA, wherein said housing comprises abase at the lower side and a cover at the upper side, and wherein aprinted circuit board includes at least electronic components thatconstitute said electronic circuitry, said printed circuit board beinglocated along either one inner wall surface or both respective innerwall surfaces of said base and said cover, wherein said electroniccomponents are separated into one group processing at least analogsignals and another group processing only digital signals, and whereinthe former group is mounted on either one of upper and lower sides ofsaid printed circuit board, while the latter group is mounted on theother of the upper side and lower side thereof, separately to eachother.
 33. A disk drive for insertion into a slot formed in an externalapparatus, said slot having a size for receiving an IC memory cardtherein, said disk drive comprising:a housing, an inside of the housingincludinga disk that stores information; a disk driving means thatforces said disk to rotate and that includes a motor having a stator ina position inside an outer diameter of said disk; a head assembly thatperforms read/write operations on said disk; and electronic circuitrythat includes at least one interface circuit which is specified by aspecification of PCMCIA-ATA; and at least one connector, that isconnected to said electronic circuitry, is fixed outside said housing,wherein a whole outer dimensions including said housing and said atleast one connector are a same as a specification of type II of PCMCIAhaving a thickness of 5 mm which is compatible in size with a size ofthe IC memory card, wherein said housing comprises a base at the lowerside and a cover at the upper side, and wherein a printed circuit boardincludes at least electronic components that constitute said electroniccircuitry, said printed circuit board being located along either oneinner wall surface or both respective inner wall surfaces of said baseand said cover, wherein said electronic components are separated intoone group processing at least analog signals and another groupprocessing only digital signals, and wherein the former group is mountedon either one of upper and lower sides of said printed circuit board,while the latter group is mounted on the other of the upper side andlower side thereof, separately to each other.
 34. A disk drivecomprising:a housing for an IC memory card which is specified by aspecification of type II of PCMCIA, an inside of said housing includingadisk that stores information, a disk driving means that forces said diskto rotate, a head assembly that perform read/write operation on saiddisk, and electronic circuitry that includes at least one interfacecircuit which is specified by the specification of PCMCIA-ATA; and atleast one connector, that is connected to said electronic circuitry, isfixed outside said housing, wherein said housing comprises a base at thelower side and a cover at the upper side, and wherein a printed circuitboard includes at least electronic components that constitute saidelectronic circuitry, said printed circuit board being located alongeither one inner wall surface or both respective inner wall surfaces ofsaid base and said cover, wherein said electronic components areseparated into one group processing at least analog signals and anothergroup processing only digital signals, and wherein the former group ismounted on either one of upper and lower sides of said printed circuitboard, while the latter group is mounted on the other of the upper sideand lower side thereof, separately to each other.
 35. A disk drivecomprising:a housing for an IC memory card which is specified by aspecification of type II of PCMCIA, said housing including a cover and abase which are made of iron and formed by a press forming process, aninside of said housing includinga disk that stores information, a diskdriving means that forces said disk to rotate, a head assembly thatperform read/write operations on said disk, and electronic circuitrythat includes at least one interface circuit which is specified by thespecification of PCMCIA-ATA; and at least one connector, that isconnected to said electronic circuitry, is fixed outside said housing,wherein said housing comprises a base at the lower side and a cover atthe upper side, and wherein a printed circuit board includes at leastelectronic components that constitute said electronic circuitry, saidprinted circuit board being located along either one inner wall surfaceor both respective inner wall surfaces of said base and said cover,wherein said electronic components are separated into one groupprocessing at least analog signals and another group processing onlydigital signals, and wherein the former group is mounted on either oneof upper and lower sides of said printed circuit board, while the lattergroup is mounted on the other of the upper side and lower side thereof,separately to each other.